1.   How does vaccination work?

Vaccination conveys immunity to diseases by active immunity, which can be achieved by administration of either inactivated or live attenuated organisms or their products. Inactivated vaccines may include the whole organism (such as typhoid vaccine), the toxoid produced by the organism (such as tetanus and diphtheria vaccines), and specific antigen vaccines (such as Hib and pneumococcus). In some cases the antigen is conjugated with proteins to facilitate the immune response. Inactivated viral vaccines may include whole viruses (IPV and hepatitis A vaccine) and specific antigens (influenza and hepatitis B vaccines). Live attenuated viral vaccines include MMR, OPV and varicella vaccines.

Immunity can also be acquired passively by the administration of immunoglobulins. Such immunity is immediate and is dose related and transient.

2.  Injections

• What is the correct site for vaccination of children? Is it the thigh or the buttock? What about the arm?

The top, outer part of the thigh is the preferred site for injections for infants under the age of 12 months. The deltoid region of the upper arm is the preferred site for vaccination of children 12 months of age and older because it is associated with fewer local reactions and has sufficient muscle bulk to facilitate the injection. The buttocks should never be used because of the risk of sciatic nerve damage.

• How many injections can be given into the same leg?

Normally only one injection should be administered in each limb. However there are occasions when a child under 12 months of age may need 3 or more vaccines. In this case two injections can be given into the same leg into the vastus lateralis muscle on the same day, but the injections should be given at least 25 mm (2.5 cm) apart using separate sterile injection equipment for each vaccine administered.

3.  National Immunisation Program Schedule

• When should premature infants be vaccinated?

4.  Contraindications and precautions

• What are the absolute contraindications to further vaccination?

5.  How well do vaccines work?

• Do some children get the disease despite being vaccinated?

This is possible, since no vaccine is 100% effective. 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 vaccines differ. For example, if 100 children are vaccinated with MMR, 5 to 10 of the 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 (lung infection) or encephalitis (inflammation of the brain).

• Isn’t natural immunity better than immunity from vaccine?

While vaccine-induced immunity may diminish with time, ‘natural’ immunity, acquired by catching the disease is usually lifelong. The problem is that the wild or ‘natural’ disease has a high risk of serious illness and occasionally, death. Children or adults can be re-vaccinated (with some vaccines but not all vaccines) if their immunity from the vaccines falls to a low level. It is important to remember that vaccines are many times safer than the diseases they prevent.

• Haven’t diseases like measles, polio, whooping cough and diphtheria already disappeared from most parts of Australia? Why do we need to keep vaccinating children against these diseases?

These diseases are much less common now, but the bacteria and viruses that cause them are still present. The potential problem is kept in check by routine vaccination programs. In countries where vaccination rates have declined, the vaccine preventable diseases have 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 big outbreak of polio among a group of Dutch people who belonged to a religious group that object 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 with OPV (oral polio vaccine), which protected the rest of the Dutch community from the outbreak. 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 still occur. Vaccination has eradicated smallpox from the world, which means that smallpox vaccination no longer necessary. In the same way polio will be eradicated from the world in the next few years.

• Does homeopathic 'immunisation' work?

No. Homeopathic 'immunisation' has not been proven to give protection against infectious diseases; only conventional immunisation produces a measurable immune response. The Council of the Faculty of Homeopathy, London, issued a statement in 1993, which reads 'The Faculty of the 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.' The Executive Director of the Australian Natural Therapies Association has stated that no properly qualified natural therapist would recommend homeopathic 'immunisation' as an alternative to conventional immunisation.

6.  Vaccine safety

• How safe are vaccines?

Before vaccines are made available they are tested for safety and efficacy in clinical trials and then in mass 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 prior to marketing approval being granted.

After introduction into immunisation schedules there is 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 problems do occur after vaccines are registered for use. An example is rotavirus vaccine, which was licensed in the USA in August 1998. In pre-licensure trials, the vaccine appeared to be safe, but post-licensure surveillance detected a risk of intussusception associated with the vaccine. As soon as this risk was discovered, the vaccine was withdrawn from the market. Rotavirus vaccine was never released in Australia.

• Is there a link between vaccination and cot death (SIDS)?

Despite extensive studies, there is no evidence that vaccination causes cot deaths (cot death is also known as Sudden Infant Death Syndrome or SIDS). Deaths do occasionally occur shortly after vaccination but the relationship is simply a chance association, since SIDS tends to happen in babies of 2–6 months of age, whether they are vaccinated or not. In an American study, which compared 400 babies with cot deaths with the same number of well babies of the same age, the babies who died from SIDS were less likely to have been vaccinated in the previous 24 hours than those who did not suffer cot death. In other words, babies who were vaccinated were less likely to die from SIDS. A similar outcome was found in a case-control study conducted in the UK, in the setting of an accelerated infant immunisation program.

• Does hepatitis B vaccine cause multiple sclerosis?

There is no evidence that hepatitis B vaccine causes multiple sclerosis (MS). Concerns about hepatitis B vaccination arose from France, and the French government stopped their school-based hepatitis B vaccination program after a few reports of a possible link between hepatitis B vaccine and MS. However, when the French data were examined, the rate of MS in vaccinated people was not significantly different from the expected population rate.

With millions of vaccinations administered worldwide, it is likely that surveillance systems in some countries will receive some reports of MS that seem to be related in time to vaccinations. As with all such reports, however, they only suggest the possibility of an association. Subsequent studies have found no increase in incidence of MS, or relapse of MS, after vaccination for Hepatitis B. There is no evidence that hepatitis B vaccine can cause MS, and good evidence that it does not.

• Does vaccination cause asthma?

No. 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. Influenza vaccine is not routinely recommended for asthmatics, but is recommended for severe asthmatics, such as those requiring frequent hospitalisation.

• Do some vaccines cause Mad Cow Disease?

Variant Creutzfeld-Jakob disease (vCJD) is considered to be the human equivalent of bovine spongiform encephalopathy (BSE, also known as ’mad cow disease’). There is no evidence that any case of vCJD has resulted from the administration of any vaccine product, despite millions of doses of vaccine being administered worldwide. Concerns about the risk of transmission of this disease arose because the production of some vaccines requires bovine derivatives such as fetal bovine serum, and there is thus a theoretical risk of transmitting BSE via some vaccines. In Australia, the Therapeutic Goods Administration has confirmed that the vaccines available in this country contain bovine materials preferentially sourced from BSE-free areas, and that they undergo appropriate purification treatment. Therefore, although some vaccines carry a theoretical risk of transmissible spongiform encephalopathies, this risk is infinitesimally small (estimated at less than one in a billion).22 The benefits of vaccination are considered to far outweigh any theoretical risk of BSE transmission.

• Does MMR vaccine cause inflammatory bowel disease and autism?

In 1993, Wakefield et al (Royal Free Hospital, London) suggested an association between both the natural and vaccine types of measles virus and inflammatory bowel disease (IBD) based on a study of 25 children with Crohn’s disease. In 1998 researchers from the same group reported the occurrence of an apparently new syndrome of an unusual type of IBD in association with developmental disorders such as autism. The researchers suggested that MMR vaccine caused 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.

This study had several weaknesses. First, finding out whether or not MMR causes autism is best determined by comparing the incidence of autism in vaccinated versus unvaccinated children. However, the researcher included only vaccinated children. Second, the author claimed that gastrointestinal inflammation contributes to autism – however, in several of the cases the behavioural problems appeared before the onset of bowel disease. Furthermore, the association between vaccine and autism was primarily based on parental recall, and parents are more likely to have linked changes in behaviour with memorable events such as vaccination. The Royal Free Hospital study was conducted on a very selective group of patients, all referred to the hospital for gastrointestinal ailments, and such a case series analysis is unable to determine causal links.

In 2002 Uhlmann, Wakefield and others published a further study showing a higher rate of measles virus in the bowel of autistic children with bowel symptoms, compared to a group of children without autism. The validity of this study is difficult to assess because the study does not report key information on the characteristics and the method of selection of the cases and controls, and on laboratory methods. For example, the vaccination status of the children in the study is not known. There was no attempt to distinguish between wild-type measles virus and vaccine strain virus – nor was there any mention of whether the laboratory personnel performing the tests were aware of the immunisation status of the children whose specimens they tested.

The onset of autism and MMR vaccination may coincidentally appear associated in time because the average age at which parents report concerns about child development is 18 to 19 months, and over 90% of children receive MMR vaccine before their second birthday in the UK.11 More thorough, large epidemiological studies have found no evidence of an association.

Why are there additives in some vaccines?

• Why are there additives in some vaccines?

Additives may be necessary as either part of the production process of some vaccines, as preservatives, or to help boost the body's immune response to the vaccine (an adjuvant). These may include formaldehyde, thiomersal and aluminium.

• Formaldehyde

Formaldehyde is used during the manufacture of tetanus vaccine (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.

• Thiomersal

Thiomersal (or thimerosal) is a compound which is partly composed of mercury. 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 seafoods) and other environmental sources are also possible sources of mercury. Vaccines used in the past, such as DTP, contained only 25 µg thiomersal per dose.

Mercury causes poisoning after it reaches a certain level in the body. Whether on not it reaches a toxic level depends on the amount of mercury consumed and the persons body weight; individuals with very low body weight are usually more susceptible to poisoning 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.

In response to this theoretical concern, all vaccines on the current ASVS for children under the age of 5 years are now either free of thiomersal, or contain a reduced (trace) amount of thiomersal. Hepatitis B containing vaccines which do not contain any thiomersal include preservative-free paediatric formulation of H-B-Vax II (which is recommended for administration in newborns and infants), and the infant and childhood vaccines, such as Infanrix Hep B, Comvax and Twinrix Junior (360/60).

People sometimes ask why thiomersal was removed from vaccines if it did not cause adverse health effects in children. There were two main reasons; first, it was an attempt to reduce to a minimum the amount of mercury given, in any form, to very small premature babies with low birth weight in whom there was a theoretical risk. Second, the intent was to reduce total exposure to mercury in babies and young children in a world where other environmental sources may be more difficult to eliminate.

• Aluminium

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 immunisation by keeping antigens near the injection site so that they can be readily accessed by cells responsible for inducing an immue 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 is 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.

Where can I get more information about vaccination? 

More information about vaccination can be found in the following publications published by the Commonwealth Department of Health and Family Services:

References