The Australian Immunisation Handbook 10th Edition
This appendix contains information for providers to refer to when responding to questions and concerns about immunisation. It covers general questions on adult and childhood vaccination, including contraindications and precautions. In addition, a discussion on some of the more recent concerns about vaccination is included, covering issues relating to vaccine safety, vaccine content, immunisation as a possible cause of some illnesses of uncertain origin, and the need for vaccination.
This appendix is divided into six sections:
- General questions
- Questions about contraindication and precautions
- Questions about vaccine safety
- Questions about vaccine content
- Questions about the need for immunisation
- Further information about vaccination
A.4.1 General questions
How does vaccination work?
When a healthy person becomes infected with a virus or bacteria (also known as a pathogen), for example, the measles virus, the body recognises the virus as an invader, produces antibodies that eventually destroy the virus, and recovery occurs. If contact with the measles virus occurs again in the future, the body’s immune system ‘remembers’ the measles virus and produces an increase in antibodies to destroy this pathogen.
Vaccination is the process that is used to stimulate the body’s immune system in the same way as the real pathogen or disease would, but without causing the symptoms of the disease. Most vaccines provide the body with ‘memory’ so that an individual does not get the disease if exposed to it (refer to 1.5 Fundamentals of immunisation).
Vaccination conveys immunity to diseases by a process called active immunity, which can be achieved by administration of either inactivated (i.e. not live) or live attenuated pathogens or their products. Live vaccines are attenuated, or weakened, by growing the organism through serial culturing (or passaging) steps in various tissue culture media. Inactivation is usually done using heat or formalin (sometimes both). Inactivated vaccines may include the whole pathogen (such as oral cholera vaccine), the toxin produced by the pathogen (such as tetanus and diphtheria vaccines), or specific antigens (such as Haemophilus influenzae type b [Hib], meningococcal and pneumococcal vaccines). In some cases, the antigen is conjugated (i.e. chemically linked) with proteins to facilitate the immune response. Inactivated viral vaccines may include whole viruses (such as inactivated poliomyelitis vaccine [IPV] and hepatitis A vaccines) or specific antigens (such as influenza and hepatitis Bvaccines). Live attenuated viral vaccines include measles-mumps-rubella (MMR), varicella and yellow fever vaccines.
Immunity can also be acquired passively by the administration of immunoglobulins, which are the same as antibodies (refer to 1.5 Fundamentals of immunisation). Such immunity is immediate and is dose-related and transient. For example, measles or hepatitis B immunoglobulin can be used promptly after exposure in an unimmunised person to help reduce the chance of getting measles or hepatitis B disease from the exposure.
What is the correct site for vaccination?
The top, outer part of the thigh (the vastus lateralis muscle) is the recommended site for injections for infants <12 months of age. The deltoid region of the upper arm is the recommended site for vaccination of all persons aged ≥12 months, because it is associated with fewer local reactions and, in younger children, has sufficient muscle bulk to facilitate the injection. However, the vastus lateralis muscle can also be used in both young children and, where absolutely necessary, adults.
Rotavirus vaccines are administered by the oral route and must never be injected.
How many injections can be given into the same limb, particularly in a
child aged <12 months?
More than one vaccine can be safely administered into a limb at the same immunisation visit in either children or adults (Refer to 2.2.9 Administering multiple vaccine injections at the same visit).
Where more than one injection is required into the one limb, the injections should be given at least 25 mm (2.5 cm) apart. Use separate sterile injection equipment for each vaccine administered. The accompanying documentation should indicate clearly which vaccines were given into which site (e.g. left arm upper/left arm lower).
Most Australian states and territories have routine immunisation schedules that include at least two injections during the primary course for children <12 months of age. In this case, injections can be given into either the same leg, into the vastus lateralis muscle, or the second injection can be given into the other vastus lateralis muscle; an alternative is the ventrogluteal site.
When should preterm infants be vaccinated?
Babies born at <32 weeks gestation or <2000 g birth weight should receive their 1st dose of hepatitis B vaccine either at birth (within the first few days of life) or at 2 months of age. The routine 2-month vaccines containing the antigens diphtheria-tetanus-acellular pertussis-hepatitis B-inactivated poliovirus-Haemophilus influenzae type b (DTPa-hepB-IPV-Hib), Streptococcus pneumoniae (13vPCV) and rotavirus should be given 2 months after birth as normal, unless an infant is very unwell. ‘Very unwell’ can be interpreted in many ways, but, in general, reflects that the premature neonate is particularly medically unstable. Delaying the 2-month vaccines is rarely required. If any preterm infant has the 2-month vaccines delayed, it should be remembered that the subsequent infant doses can be given 1 month apart rather than 2 months. Hence, if an infant receives the 2-month vaccines at 3 months of age then the 4-month vaccines should still be given at 4 months of age. However, the 3rd dose of DTPa-hepB-IPV-Hib should not be given before 6 months of age. Further explanation of the special immunisation needs of premature babies is provided in 3.3.2 Vaccination of women who are planning pregnancy, pregnant or breastfeeding, and preterm infants.
Do elderly people (>65 years) who have no chronic illnesses need the
Yes. Age is an independent risk factor for severe influenza. Vaccination of those aged >65 years, regardless of the presence or absence of chronic illness, reduces mortality during the winter period in this age group (refer to 4.7 Influenza). The healthy elderly should also receive the 23-valent pneumococcal polysaccharide vaccine (refer to 4.13 Pneumococcal disease).
Should adults receive pertussis (whooping cough) vaccine boosters?
Yes. dTpa vaccine (which protects against pertussis and also tetanus and diphtheria) is recommended in Australia for booster vaccination of individuals ≥10 years of age who have previously had a primary course of diphtheria-tetanus-pertussis vaccine. dTpa vaccines have a lower content of diphtheria and pertussis antigens than DTPa formulations for young children.
A randomised control trial has shown that a single booster dose in adults achieves high levels of protection against pertussis.1 However, the few studies which look at how long immunity lasts following a single booster dose suggest a decline out to 10 years (refer to 4.12 Pertussis).
A single dose of dTpa is recommended for the following groups, unless contraindicated or if they have already received a previous dose of dTpa in the last 10 years (or shorter intervals where specifically indicated, refer to 4.12 Pertussis):
- adults working with infants and young children <4 years of age such as staff working in early childhood education and care
- all healthcare workers
- pregnant women during the third trimester of each pregnancy (ideally between 28 and 32 weeks)
- adult household contacts and carers (e.g. fathers and grandparents) of infants <6 months of age, ideally at least 2 weeks before beginning close contact with the infant
- adults ≥65 years of age
- any adult expressing an interest in receiving a booster dose of dTpa.
These recommendations are based on the available evidence on waning immunity following pertussis booster vaccines and the groups who are most at risk of pertussis or who are in contact with those at greatest risk of pertussis. No recommendations on the need for further dTpa booster doses for other groups have been made at this time.
dTpa vaccine should also be used in place of dT at the age routinely recommended for a tetanus and diphtheria booster (50 years) if dTpa has not been received in the previous 10 years.
A person wants to receive his/her vaccines separately. Why can’t they do this?
There is no scientific evidence or data to suggest that there are any benefits in receiving vaccines such as MMR as separate monovalent vaccines. Using the example of MMR vaccine, there is no individual mumps, measles or rubella vaccine approved for use in Australia. If these vaccines were to be administered individually, it would require three separate vaccines, which would unnecessarily increase discomfort for the child. In addition, if these monovalent vaccines were not given on the same day, they would need to be spaced 1 month or more apart, which would increase the risk of that person being exposed to serious vaccine-preventable diseases. A policy of providing separate vaccines would cause some people to not receive the entire course. Combination vaccines can offer a reduced amount of vaccine preparation to be injected overall, compared to three individual vaccine doses.
Is vaccination compulsory? What happens if children do not get vaccinated?
Vaccination is not compulsory in Australia.
However, a parent’s eligibility to receive government family assistance payments including Family Tax Benefit Part A supplement, Child Care Benefit and Child Care Rebate is linked to their child’s immunisation status until the end of the calendar year they turn 19 years of age. To meet the immunisation requirements for these family assistance payments, parents need to ensure their child is up-to-date with age-appropriate immunisations according to the early childhood vaccination schedule or have commenced a suitable catch-up schedule dependent on the child’s age.
A child, adolescent or young adult less than 20 years of age can be granted exemption from the required vaccines if there is a medical reason. To meet immunisation requirements for family assistance payments your general practitioner will need to provide the Immunisation Register with a completed ACIR Immunisation Medical Exemption form.
More information on immunisation requirements for family assistance payments can be found on the Australian Government Department of Human Services website.
Day-care centres and schools also have vaccination requirements; however, these vary according to state and territory legislation and may include requiring documentation of vaccination for enrolment, to needing to keep unvaccinated children at home until the incubation period for that particular disease has passed or no further cases have occurred in that setting.
A4.2 Questions about contraindications and precautions
If a person has any concerns about whether to proceed with vaccination, they should be provided with appropriate information and encouraged to obtain expert advice from their usual immunisation provider or an immunisation specialist, if necessary. Refer to Appendix 1 Contact details for Australian, state and territory government health authorities and communicable disease control for contact details.
What are the absolute contraindications to childhood vaccination?
True contraindications to vaccines are extremely rare (refer to relevant chapters), and include only anaphylaxis to any of the particular vaccine’s components, and anaphylaxis following a previous dose of that vaccine. Follow-up specialist medical advice should always be sought if any severe reaction or anaphylaxis has occurred following the administration of any vaccine(s).
Note: Anaphylaxis following ingestion of eggs does not contraindicate MMR vaccine, as the vaccine viruses are not grown in eggs and the vaccine does not contain any egg protein (refer to 4.9 Measles). Many persons who have a history of a severe allergic reaction to eggs can also be vaccinated with influenza vaccine (refer to 4.7 Influenza).
Can someone who has had whooping cough (pertussis) still be vaccinated?
Vaccination with pertussis vaccine in children, adolescents or adults who have had laboratory-confirmed pertussis infection is safe and is necessary, as natural immunity does not confer life-long protection. In particular, incompletely vaccinated infants <6 months of age who develop pertussis may not mount an adequate immune response following infection and should receive all routinely scheduled vaccines, including pertussis-containing vaccines (refer to 4.12 Pertussis).
What are the precautions to vaccination?
In general, persons with impaired immunity or on immunosuppressive therapy, or pregnant women, should not be given live vaccines. However, any general concerns that the person to be vaccinated or the parent/carer holds should always be fully discussed prior to the administration of any vaccine.
Should a person with an intercurrent illness be vaccinated?
A child or adult with a minor illness (without systemic illness and with a temperature <38.5°C) may be safely vaccinated. People, including infants, toddlers and teenagers with minor coughs and colds without fever, or those receiving antibiotics in the recovery phase of an acute illness, can be vaccinated safely and effectively. In a person with a major illness or high fever ≥38.5°C, vaccination should be postponed until they are well. If vaccination were to be carried out during such an illness, the fever might be confused with vaccine side effects and might also increase discomfort to the person. In such cases, it is advisable to defer vaccination and arrange for the person to return for vaccination when well again (refer to Table 2.1.2 Responses to relevant conditions or circumstances identified by the pre-vaccination screening checklist).
Should persons with epilepsy be vaccinated?
Yes. Stable neurological conditions (such as epilepsy) are not a reason to avoid giving any vaccines, including pertussis (whooping cough) (refer to 4.12 Pertussis). A family history of fits or epilepsy is not a reason to avoid vaccination.
Febrile seizures, a relatively common response to fever in all young children, can occur at a low rate following immunisation. A history of febrile seizure of any cause is not a reason to avoid future vaccines.
The administration of paracetamol at the time of, or immediately after, vaccination to reduce the risk of fever is not routinely recommended, with the exception of specific recommendations for meningococcal B vaccine in infants <2 years of age (refer to 4.10 Meningococcal disease). However, if an infant, child or adult has a fever of >38.5°C following vaccination or has pain at the injection site, paracetamol can be given (refer to 2.3.2 Adverse events following immunisation).
Should persons with a neurological disease or conditions receive the normal vaccination schedule?
Yes. Persons with a neurological disease are often at increased risk of complications from diseases like measles, influenza and whooping cough, as they can be more prone to respiratory infections and chest problems. It is important that these children be immunised, on time, as recommended in the National Immunisation Program schedule.
Are steroids a contraindication to vaccination?
Live vaccines, such as MMR, measles-mumps-rubella-varicella (MMRV), bacille Calmette-Guérin (BCG) and varicella-zoster vaccines, should not be given to children or adults receiving high-dose oral or parenteral corticosteroid therapy for more than 1 week. High-dose oral corticosteroid therapy is defined as more than 2 mg/kg per day prednisolone for more than 1 week in children, or more than 60 mg per day for more than 1 week in adults. This is because steroids, in large doses, greatly suppress the immune system, which means that, not only is the vaccine unlikely to be effective, but there is an increased chance of an adverse event occurring as a result of the immunosuppression (refer to 3.3.3 Vaccination of immunocompromised persons).
Inactivated vaccines, for example, DTPa-hepB-IPV-Hib or hepatitis B, may be less effective in this group, but are not contraindicated. Therapy with inhaled steroids is not a contraindication to vaccination.
Should vaccines be given to persons who have problems with their
Persons who are immunocompromised (from either a disease or medical treatment) should generally not be given live viral vaccines such as MMR, MMRV, varicella, zoster or rotavirus vaccines (refer to 4.9 Measles, 4.22 Varicella, 4.24 Zoster and 4.17 Rotavirus).
HIV-infected persons may be given MMR, varicella and zoster vaccines, provided they do not have severe immunocompromise (refer to 3.3 Groups with special vaccination requirements and Table 3.3.4 Categories of immunocompromise in HIV-infected persons, based on age-specific CD4+ counts and percentage of total lymphocytes). The close contacts of persons who are immunocompromised can be given live viral vaccines, except oral polio vaccine, which is no longer used in Australia.
The rash seen in a small percentage of MMR vaccine recipients, usually between 5 and 12 days after vaccination, is not infectious. Non-immune household contacts of persons who are immunocompromised should receive varicella vaccine. There is an almost negligible risk of transmitting varicella vaccine virus from a vaccine-related vesicular rash to contacts. However, vaccine-related rash occurs in 3 to 5% of vaccinated persons, either locally at the injection site or generalised, with a median of only 25 lesions. This small infection risk of the less virulent attenuated vaccine strain is far outweighed by the high risk of non-immune contacts catching wild varicella infection and transmitting the virus to the immunocompromised household member via respiratory droplets or from the large number of skin lesions that occur with wild varicella infection (a median of 300 to 500 lesions).
Live viral vaccines can be given to persons with leukaemia and other malignancies at least 3 months after they have completed chemotherapy, provided there are no concerns about their immune status. Such measures would normally be carried out under the supervision of the person’s oncologist (refer to 3.3.3 Vaccination of immunocompromised persons).
What vaccines should someone with HIV infection receive?
Persons with HIV (human immunodeficiency virus) infection, especially children, should have all routine inactivated vaccines on the National Immunisation Program schedule. Varicella vaccine is contraindicated in persons with HIV who are significantly immunocompromised, as it can cause disseminated varicella infection. However, it may be considered for asymptomatic or mildly symptomatic HIV-infected children, after weighing up the potential risks and benefits. This should be discussed with the child’s specialist. MMR vaccine can be given to children with HIV, depending on their CD4+ counts (refer to ‘Should vaccines be given to persons who have problems with their immune systems?’ above). Persons with HIV infection should also be vaccinated against pneumococcal disease (refer to 4.13 Pneumococcal disease). Influenza vaccine is also recommended for HIV-infected persons. They should not be given BCG, due to the risk of disseminated infection. More detailed information on the use of vaccines in persons with HIV is included in 3.3.3 Vaccination of immunocompromised persons.
Should chronically ill persons be vaccinated?
In general, persons with chronic diseases should be vaccinated as a matter of priority, because they are often more at risk from complications from vaccine-preventable diseases. Annual influenza vaccine is highly recommended for chronically ill persons and their household contacts.
Care is needed with the use of live attenuated viral vaccines in situations where the person’s illness, or its treatment, may result in impaired immunity. Advice may need to be sought on these patients to clarify the safety of live viral vaccine doses.
Should children or household contacts be vaccinated while the child’s
mother is pregnant?
There is no problem with giving routine vaccinations to a child, or others, living in the same household with a pregnant woman. MMR vaccine viruses are not transmissible. Administration of varicella vaccine to household contacts of non-immune pregnant women is safe. Transmission of varicella vaccine virus is very rare. There is an almost negligible risk of transmitting varicella vaccine virus from a vaccine-related vesicular rash to contacts. However, vaccine-related rash occurs in 3 to 5% of vaccinated persons, either locally at the injection site or generalised, with a median of only 25 lesions. Furthermore, vaccinating the child of a pregnant mother will reduce the risk of her being infected by her offspring with the more virulent wild virus strain if she is not immune (refer to 3.3.2 Vaccination of women who are planning pregnancy, pregnant or breastfeeding, and preterm infants).
Should persons with allergies be vaccinated? What precautions are required for atopic or egg-sensitive children or adults?
Depending on the allergy identified, there often may not be a contraindication to vaccination. Specialist medical advice should always be sought in order to determine which vaccinations can be safely given. For example, a history of an allergy to antibiotics most commonly relates to β-lactam, or related antibiotics, and is not a contraindication to vaccines that contain neomycin, polymyxin Bor gentamicin. Previous reactions to neomycin that only involved the skin are not considered a risk factor for a severe allergic reaction or anaphylaxis to vaccines manufactured with neomycin, since there are only trace amounts of this antibiotic in the final product (refer to 3.3.1 Vaccination of persons who have had an adverse event following immunisation).
For other allergies, refer to Appendix 3, Components of vaccines used in the National Immunisation Program, and the relevant vaccine product information (PI) enclosed in the vaccine package. Unless the person being vaccinated has an allergy to a specific constituent of a vaccine (or has another contraindication), there is no reason not to vaccinate. Asthma, eczema and hay fever are not contraindications to any vaccine, unless the child/adult is receiving high-dose oral steroid therapy.
Persons with egg allergies can receive MMR vaccines because the measles and mumps components of MMR vaccine do not contain sufficient amounts of egg ovalbumin to contraindicate MMR vaccination of people with egg allergy (even anaphylaxis) (refer to 3.3.1 Vaccination of persons who have had an adverse event following immunisation and 4.9 Measles). A simple dislike of eggs, or having diarrhoea or stomach pains after eating eggs, are not reasons to avoid MMR vaccination, and no special precautions are required in these circumstances. These persons can also have all other routine vaccines without special precautions.
A history of anaphylaxis or allergy to egg had previously been considered an absolute contraindication to influenza vaccination, but there have now been a number of studies indicating that the majority of such persons can be safely vaccinated.2,3 Given that there is still a small risk of anaphylaxis, it is essential that such persons are vaccinated in facilities with staff able to recognise and treat anaphylaxis. (Refer also to 4.7 Influenza.)
Yellow fever, Q fever and one of the available rabies vaccines contain a higher amount of egg albumin than is present in the currently available influenza vaccines. Persons with egg allergy requiring vaccination with either yellow fever, rabies or Q fever vaccines, should seek specialist immunisation advice from their state or territory health department. Refer also to relevant chapters of this Handbook.
Families with questions about allergies and vaccines are encouraged to discuss this with their immunisation service provider and, where necessary, seek referral to an immunologist to have any questions promptly answered to avoid unnecessary delays of vaccine doses or referral to a specialist immunisation clinic. Information on specialist immunisation clinics is available from your local state or territory health department. (Refer to Appendix 1 for further details.)
A4.3 Questions about vaccine safety
Some people have concerns about immunisation. These mostly relate to whether the vaccine is safe and whether vaccines weaken the immune system. Providers should always listen to and acknowledge people’s concerns. Providers should discuss the risks and benefits of immunisation with parents/carers honestly and in a non-defensive manner. Parents/carers and adult vaccine recipients should receive accurate information on the risks from vaccine-preventable diseases and information about vaccine side effects and adverse events (refer to table Comparison of the effects of diseases and the side effects of NIP vaccines inside the back cover of this Handbook). The following section responds to some concerns raised about the safety of immunisation, and examines the scientific evidence in order to assist providers and parents in making an informed choice about the risks and benefits of vaccination.
How safe are vaccines?
Before vaccines are made available for general use they are tested for safety and efficacy in clinical trials and then in large trials, otherwise known as phase II (2) and III (3) trials. All vaccines marketed in Australia are manufactured according to strict safety guidelines and are evaluated by the Therapeutic Goods Administration, to ensure they are efficacious and are of adequate quality and safety, before marketing approval is granted.
After vaccines are introduced into vaccination schedules, they are subjected to continuing surveillance of efficacy and safety through trials and post-marketing surveillance. In Australia, there are regional and national surveillance systems actively seeking any adverse events following immunisation. This is necessary, as sometimes unexpected side effects occur after vaccines are registered for use. Australian reports on adverse events that occur following immunisation are published on a 6-monthly basis in the journal Communicable Diseases Intelligence (www.health.gov.au/internet/main/publishing.nsf/content/cda-pubs-cdi-cdiintro.htm).
Can too many vaccines overload or suppress the natural immune system?
No. Although the increase in the number of vaccines and vaccine doses given to children has led to concerns about the possibility of adverse effects of the aggregate vaccine exposure, especially on the developing immune system, there is not a problem. In day-to-day life, all children and adults confront enormous numbers of antigens, and the immune system responds to each of these in various ways to protect the body. Studies of the diversity of antigen receptors indicate that the immune system can respond to an extremely large number of antigens. In addition, the number of antigens received by children during routine childhood vaccination has actually decreased compared with several decades ago. This has occurred in spite of the increase in the total number of vaccines given, and can be accounted for by the removal of two vaccines – smallpox vaccine (which contained about 200 different proteins), and whole-cell pertussis vaccine (about 3000 distinct antigenic components) from routine vaccination schedules. In comparison, the acellular pertussis vaccine currently used in Australia has only 3 to 5 pertussis antigens.4
Do vaccines cause disease?
Some studies have suggested a temporal link between vaccinations and certain medical conditions, such as asthma, multiple sclerosis and diabetes. The questions of a link are often made for a disease of unknown cause. The appearance of a certain medical condition after vaccination does not necessarily imply that they are causally related. Importantly, however, once an issue is raised it needs prompt research, discussion and then education to avoid creating a myth. In many cases, subsequent epidemiological studies have indicated that the association is due to chance alone. The following is a list of concerns that have been raised.
Does MMR vaccine cause inflammatory bowel disease or autistic spectrum disorder?
In 1998, Wakefield et al. (Royal Free Hospital, London) published a case-series study with 12 children suggesting that MMR vaccine caused inflammatory bowel disease (IBD), which then resulted in decreased absorption of essential vitamins and nutrients through the intestinal tract. They proposed that this could result in developmental disorders such as autism. The Lancet retracted this publication in 2010 and the British Medical Council struck off the lead author in 2010, following the British General Medical Council’s Fitness to Practice Panel finding the author ‘guilty of serious professional misconduct’.
An extensive review published in 2004 by the Institute of Medicine (IOM), an independent expert body in the United States, concluded that there is no association between the MMR vaccine and the development of autism. A 2011 update by the IOM continues to reject any causal association between MMR vaccine and autism.
Refer to 4.9 Measles for further information. There is also an MMR vaccine decision aid designed for parents.
Do childhood immunisations cause asthma?
There is no evidence that vaccination causes or worsens asthma. It is especially important that children with asthma be vaccinated like other children, as catching a disease like whooping cough can make an asthma attack worse. Although influenza vaccine is not routinely recommended for all asthmatics, it is recommended for severe asthmatics, such as those requiring frequent hospitalisation (refer to 4.7 Influenza).
Does influenza vaccine cause flu?
No. It is not possible for influenza vaccine to cause ‘flu’ as it is not a live viral vaccine. (Note: a live attenuated influenza vaccine is used in some countries, but not in Australia.) As some people experience side effects such as a mild fever after the vaccine, it is understandable that they may confuse these symptoms with actually having the flu. In addition, the influenza vaccine is recommended to be given at the commencement of the flu season. Hence, it is possible that a person who has contracted, and is incubating, influenza during vaccination will mistakenly believe the vaccine to be causal. In addition, influenza vaccine is given at the very time of year when there are a lot of upper respiratory tract infections (URTIs) around. It is not uncommon for someone to attribute an URTI within a week of an influenza vaccine to the vaccine dose. Importantly, URTI symptoms occurring after influenza vaccine should not put people off having the vaccine the following year.
A4.4 Questions about vaccine content5
Refer also to Table A3.1 Components of vaccines used in the National Immunisation Program in Appendix 3. Refer also to the product information (PI) or the consumer medicines information (CMI) for individual vaccines; both are available from the TGA website.
Preservatives are used to prevent fungal and or bacterial contamination of the vaccine. They include thiomersal, phenoxyethanol and phenol.
Thiomersal (or thimerosal) is a compound that is partly composed of a form of mercury called ethylmercury. It has been used in very small amounts in vaccines for about 60 years to prevent bacterial and fungal contamination of vaccines. In the past, the small amount of thiomersal in vaccines was one of several potential sources of mercury. Diet (such as some seafood) and other environmental sources are also possible sources of mercury. Vaccines used in the past, such as DTP, contained only 25 µg of thiomersal per dose.
Mercury causes a toxic effect after it reaches a certain level in the body. Whether or not it reaches a toxic level depends on the amount of mercury consumed and the person’s body weight; individuals with very low body weight are usually more susceptible to toxic effects from a certain intake of mercury. Thus, the possibility existed that vaccination of newborn babies, particularly those of very low birth weight, with repeated doses of thiomersal-containing vaccines might have resulted in levels of mercury above the recommended guidelines.
Thiomersal was removed from vaccines in response to the above theoretical concern and to reduce total exposure to mercury in babies and young children in a world where other environmental sources may be more difficult to eliminate.6-8
Currently, all vaccines on the NIP for children and adolescents are free of thiomersal.
The aromatic ether alcohol, 2-phenoxyethanol, is used as a preservative in many vaccines, and also as a preservative in cosmetics. It is used in vaccines as an alternative preservative to thiomersal.
Phenol is an aromatic alcohol used as a preservative in a few vaccines.
Adjuvants are compounds used to enhance the immune response to vaccination and include various aluminium salts, such as aluminium hydroxide, aluminium phosphate and potassium aluminium sulphate (alum). A review of all available studies of aluminium-containing diphtheria, tetanus and pertussis vaccines (either alone or in combination) found no evidence that aluminium salts in vaccines cause any serious or long-term adverse events.9
A small amount of aluminium salts has been added to some vaccines for about 60 years. Aluminium acts as an adjuvant, which improves the protective response to vaccination by keeping antigens near the injection site so they can be readily accessed by cells responsible for inducing an immune response. The use of aluminium in vaccines means that, for a given immune response, less antigen is needed per dose of vaccine, and a lower number of total doses are required. Although aluminium-containing vaccines have been associated with local reactions and, less often, with the development of subcutaneous nodules at the injection site, other studies have reported fewer reactions with aluminium-adsorbed vaccines than with unadsorbed vaccines. Concerns about the longer-term effects of aluminium in vaccines arose after some studies suggested a link between aluminium in the water supply and Alzheimer’s disease, but this link has never been substantiated. The amount of aluminium in vaccines is very small and the intake from vaccines is far less than that received from diet or medications such as some antacids.10,11
Additives are used to stabilise vaccines in adverse conditions (temperature extremes of heat and freeze drying) and to prevent the vaccine components adhering to the side of the vial.
Examples of additives include:
- lactose and sucrose (both sugars)
- sorbitol and mannitol (both sugar alcohols)
- polysorbate 80, made from sorbitol and oleic acid (an omega fatty acid)
- glycine and monosodium glutamate or MSG (both are amino acids or salts of amino acids)
- gelatin, which is partially hydrolysed collagen, usually of bovine or porcine origin.
Some members of the Islamic and Jewish faiths may object to vaccination, arguing that vaccines can contain pork products. However, scholars of the Islamic Organization for Medical Sciences have determined that the transformation of pork products into gelatin will sufficiently alter them, thus making it permissible for observant Muslims to receive vaccines, even if the vaccines contain porcine gelatin. Likewise, leaders of the Jewish faith have also indicated that pork-derived additives to medicines are permitted. Further information may be obtained from the following websites Vaccine Safety (www.vaccinesafety.edu/Porcine-vaccineapproval.htm) and Immunisation Action Coalition (www.immunize.org/concerns/porcine.pdf)
- human serum albumin (protein).
Manufacturing residuals are residual quantities of reagents used in the manufacturing process of individual vaccines. They include antibiotics (such as neomycin or polymyxin), inactivating agents (e.g. formaldehyde) as well as cellular residuals (egg and yeast proteins), traces of which may be present in the final vaccine. Antibiotics are used during the manufacturing process to ensure that bacterial contamination does not occur; traces of these antibiotics may remain in the final vaccine. Inactivating agents are used to ensure that the bacterial toxin or viral components of the vaccine are not harmful, but will result in an immune response. Cellular residuals are minimised by extensive filtering. However, trace amounts may be present in the final product. The most commonly found residual is formaldehyde.
Formaldehyde is used during the manufacture of many vaccines. For example, with tetanus vaccines, formaldehyde is used to detoxify the tetanus toxin protein produced. The non-toxic protein, which becomes the active ingredient of the vaccine, is further purified to remove contaminants and any excess (unreacted or unbound) formaldehyde. The current standard applicable to vaccines for human use in Australia is less than 0.02% w/v of free formaldehyde. The maximum amount of free formaldehyde detected by the Therapeutic Goods Administration during testing of vaccines registered in Australia has been 0.004% w/v, which is well below the standard limit.
Other ingredients and information about manufacturing
Vaccines also may be made up in sterile water or sterile saline (salt-water).
Some viruses used in vaccines require the use of ‘cell lines’ in which to grow the vaccine virus. The cell lines are not included as a component of the vaccine. Some of these cell lines (called human diploid cell lines – WI-38 and MRC-5) were originally derived from human fetal tissue in the 1960s. These cell lines have been growing under laboratory conditions for more than 40 years, and there has been no further fetal tissue obtained since the 1960s. The vaccines manufactured using viruses that were grown in these cell lines include rubella vaccine and MMR vaccine, hepatitis A vaccines, varicella vaccines, rabies vaccine and oral polio (Sabin) vaccine (no longer available in Australia). Many of these vaccines prevent severe disease in unborn babies and infants, including, most notably, rubella, which causes congenital rubella syndrome.
A4.5 Questions about the need for immunisation
Isn’t natural immunity better than immunity from vaccination?
While vaccine-induced immunity may diminish with time without boosters (vaccine or contact with wild-type infection), ‘natural’ immunity, acquired by catching the disease, is usually life-long, with the exception of pertussis. The problem is that the wild or ‘natural’ disease has a higher risk of serious illness and occasionally death. Children or adults can be revaccinated (with some, but not all, vaccines) if their immunity from the vaccines falls to a low level or if previous research has shown that a booster vaccination is required for long-term protection. It is important to remember that vaccines are many times safer than the diseases they prevent.
Diseases like measles, polio and diphtheria have already disappeared from most parts of Australia. Why do we need to keep vaccinating children against these diseases?
Although these diseases are much less common now, they still exist. The potential problem of disease escalation is kept in check by routine vaccination programs. In countries where vaccination rates have declined, vaccine-preventable diseases have sometimes reappeared. For example, Holland has one of the highest rates of fully vaccinated people in the world. However, in the early 1990s, there was a large outbreak of polio among a group of Dutch people who belonged to a religious group that objected to vaccination. While many of these people suffered severe complications like paralysis, polio did not spread into the rest of the Dutch community. This was due to the high rate of vaccination against polio, which protected the rest of the Dutch community.
There have been recent outbreaks of whooping cough, measles and rubella in Australia, and a number of children have died. Cases of tetanus and diphtheria, although rare, still occur. Thus, even though these diseases are much less common now than in the past, it is necessary to continue to protect Australian children, so that the diseases cannot re-emerge to cause large epidemics and deaths.
Also, many of the diseases against which we vaccinate our children are still common in other areas of the world. For example, measles still occurs in many Asian countries, where many people take holidays or travel for business. Therefore, it is possible for non-immune individuals to acquire measles overseas, and, with the speed of air travel, arrive home and be able to pass measles onto those around them if they are unprotected. Measles is highly infectious and can infect others for several hours after an infected person has left a room. Vaccination, while not 100% effective, can considerably minimise a person’s chance of catching a disease. The more people who are vaccinated, the less chance there is that a disease, such as measles, will spread widely in the community. This is referred to as ‘herd immunity’.
Why do some children get the disease despite being vaccinated?
This is possible because a small proportion of those who are vaccinated will remain susceptible to the disease. However, in the cases in which illness does occur in vaccinated individuals, the illness is usually much less severe than in those who were not vaccinated. The protection provided by the same vaccine to different individuals can differ. For example, if 100 children are vaccinated with MMR, 5 to 10 of the 100 fully vaccinated children might still catch measles, mumps or rubella (although the disease will often be less severe in vaccinated children). If 100 children are vaccinated with a full schedule of pertussis-containing vaccines, 20 of the children might still get whooping cough, but, once again, the disease is often less severe in these vaccinated children. To put it another way, if you do not vaccinate 100 children with MMR vaccine, and the children are exposed to measles, all of them will catch the disease with a risk of high rates of complications like pneumonia or encephalitis. The reason why fewer children become infected than these figures suggest is due to the high vaccine coverage rates in the community. If there are high coverage rates, there is less chance of contact with the infection and, although some children may be susceptible, they have a low chance of contact with the infection (this situation is also called ‘herd immunity’).
What about homeopathic ‘immunisation’?
Homeopathic ‘immunisation’ has not been proved to give protection against infectious diseases; only conventional vaccination produces a measurable immune response. The Council of the Faculty of Homeopathy, London, issued a statement in 1993, which reads: ‘The Faculty of Homeopathy, London, strongly supports the conventional vaccination program and has stated that vaccination should be carried out in the normal way, using the conventional tested and proved vaccines, in the absence of medical contraindications’.12
A4.6 Further information about vaccination
More information about vaccination can be found in the following publications produced by the Australian Government Department of Health:
- Understanding childhood immunisation
- Immunisation myths and realities – responding to arguments against immunisation: a guide for providers.
The following two websites include further publications, fact sheets, etc. and are recommended for both immunisation service providers and the general public:
- Immunise Australia website
- The National Centre for Immunisation Research and Surveillance of Vaccine Preventable Diseases (NCIRS) website
Also, check with your local state or territory Public Health Unit or local council, maternal child health nurse or public health vaccination clinic for more information (refer to Appendix 1 Contact details for Australian, state and territory government health authorities and communicable disease control).
- Ward JI, Cherry JD, Chang SJ, et al. Efficacy of an acellular pertussis vaccine among adolescents and adults. New England Journal of Medicine 2005;353:1555-63.
- Australasian Society of Clinical Immunology and Allergy (ASCIA). Guidelines for medical practitioners: Influenza vaccination of the egg-allergic individual. 2010. Available at: (www.allergy.org.au/health-professionals/papers/influenza-vaccination-of-the-egg-allergic-individual) (accessed July 2011).
- Greenhawt MJ, Li JT, Bernstein DI, et al. Administering influenza vaccine to egg allergic recipients: a focused practice parameter update. Annals of Allergy, Asthma and Immunology 2011;106:11-6.
- Offit PA, Quarles J, Gerber MA, et al. Addressing parents’ concerns: do multiple vaccines overwhelm or weaken the infant’s immune system? Pediatrics 2002;109:124-9.
- Eldred BE, Dean AJ, McGuire TM, Nash AL. Vaccine components and constituents: responding to consumer concerns. Medical Journal of Australia 2006;184:170-5.
- Centers for Disease Control and Prevention (CDC). Summary of the joint statement on thimerosal in vaccines. American Academy of Family Physicians, American Academy of Pediatrics, Advisory Committee on Immunization Practices, Public Health Service. MMWR Morbidity and Mortality Weekly Report 2000;49:622, 631.
- Immunization Safety Review Committee, Board on Health Promotion and Disease Prevention, Institute of Medicine. Stratton K, Gable A, McCormick MC, eds. Immunization safety review: thimerosal-containing vaccines and neurodevelopmental disorders. Washington, D.C.: National Academy Press, 2001.
- Ball LK, Ball R, Pratt RD. An assessment of thimerosal use in childhood vaccines. Pediatrics 2001;107:1147-54.
- Jefferson T, Rudin M, Di Pietrantonj C. Adverse events after immunisation with aluminium-containing DTP vaccines: systematic review of the evidence. The Lancet Infectious Diseases 2004;4:84-90.
- Clements CJ, Griffiths E. The global impact of vaccines containing aluminium adjuvants. Vaccine 2002;20 Suppl 3:S24-33.
- Keith LS, Jones DE, Chou CH. Aluminum toxicokinetics regarding infant diet and vaccinations. Vaccine 2002;20 Suppl 3:S13-7.
- Sulfaro F, Fasher B, Burgess MA. Homoeopathic vaccination. What does it mean? Medical Journal of Australia 1994;161:305-7.