Dr K K Aggarwal, Past President IMAS and President Elect CMAAO
Multiple studies have failed to demonstrate any association between measles, mumps, and rubella or MMR vaccination and autism or other chronic diseases. However, there is an association between congenital rubella syndrome and autism, highlighting a potential role for MMR immunisation in the prevention of autism spectrum disorders [J Pediatr 1978; 93:699.].
The prevalence of autism has increased over the last two decades. The real or perceived increase in autism cases has occurred at a time when the number of recommended childhood vaccines also have increased. Parents of children with autism have identified a temporal association between immunisations and the onset of more evident symptoms of autism in the second year of life, leading to speculation that certain vaccines constituents may play a role in the development of autism. But multiple large, well-designed epidemiologic studies and systematic reviews do not support an association between the measles, mumps, and rubella vaccine and autism.
On the other hand, the administration of childhood vaccines has led to a decline in the incidence of childhood diseases that can have severe sequelae. Withholding vaccines from a child because of a hypothetical risk places the child at risk for real infection that may have real sequelae.
The benefits of vaccines are clear. Several infectious diseases that were once associated with significant morbidity and mortality have been almost eliminated through the development, distribution, and almost universal administration of protective vaccines.
With the declining incidence of once-common vaccine-preventable diseases, parents of young children may not appreciate the potential severity or dire consequences of the illnesses. Parents who lack such appreciation may be willing to forego immunisations for their children, particularly if unproven risks are highly publicised.
When this occurs, immunisation rates decline, and outbreaks of infectious diseases, such as measles and pertussis, may occur with significant morbidity and mortality. Although the overall prevalence of complete vaccine refusal is <2 per cent substantial numbers of parents refuse one or more vaccines or request that vaccines be administered on an alternative schedule. Concern about vaccine safety is the most common reason for vaccine refusal. Other parental concerns may focus on the belief that vaccines are not necessary or freedom of choice. Remember vaccine refusal may result in vaccine-preventable disease in the individual and/or outbreaks of vaccine-preventable disease in unvaccinated and vaccinated individuals.