Current Controversies Even though vaccines are very safe and serious adverse events proven to be due to licensed vaccines are rare, the recent rise in the reporting of autism spectrum disorders has led some parents of affected children to claim that thimerosal—used as a preservative—is the cause of the problem. No study has yet implicated thimerosal or the vaccines in which it has been used as a likely cause of these disorders; however, fully 50% of cases before the Vaccine Injury Compensation Program concern autism allegedly due to mercury. In 1999, thimerosal was removed from single-dose formulations of recommended. | Chapter 116. Immunization Principles and Vaccine Use Part 11 Current Controversies Even though vaccines are very safe and serious adverse events proven to be due to licensed vaccines are rare the recent rise in the reporting of autism spectrum disorders has led some parents of affected children to claim that thimerosal used as a preservative is the cause of the problem. No study has yet implicated thimerosal or the vaccines in which it has been used as a likely cause of these disorders however fully 50 of cases before the Vaccine Injury Compensation Program concern autism allegedly due to mercury. In 1999 thimerosal was removed from single-dose formulations of recommended childhood vaccines in the United States the exception is influenza vaccine for which thimerosal-free preparations have been in short supply. There is no evidence that the frequency of autism diagnoses has changed since the discontinuation of thimerosal use but further observation is necessary. It is important to resolve these controversies particularly because it may be difficult to ensure product sterility in developing countries where multidose vials of vaccine are most cost-effective without the use of preservative. Disparities in vaccine coverage among the majority and minority communities in the United States persist. Reasons for underimmunization include limited access to health care lack of insurance assignment of a low priority to preventive measures and insufficient knowledge about vaccines and the importance of being vaccinated. The persistence of wild poliovirus in immunocompromised individuals and the reversion of live poliovirus vaccine to virulence in several communities have catalyzed debate about whether it really is possible to eradicate poliovirus from the world thus allowing the cessation of immunization or whether the best that can be hoped for is the worldwide elimination of clinical disease with continued routine immunization to keep the risk low. The addition of new .
