Reassure worried parents: Vaccines rarely have serious adverse effects

September 1, 2011

A recent consensus report gives pediatricians more ammunition when trying to persuade parents to update their children?s immunizations as school begins this year. The message was very clear: Serious adverse events associated with vaccines can occur but are very rare. The report also had some comforting information about the adverse effects (ie, autism) that parents fear most.

A recent consensus report gives pediatricians more ammunition when trying to persuade parents to update their children’s immunizations as school begins this year.

The message from the recent Institutes of Medicine (IOM) report was very clear: Serious adverse events associated with vaccines can occur but are very rare. Furthermore, there is no evidence that vaccines cause some of the adverse effects parents fear most.

Based on an analysis of more than 1,000 research articles, the committee found no evidence of a connection between the measles, mumps, and rubella (MMR) vaccine and autism. Further, neither the MMR vaccine nor the diphtheria-tetanus-acellular pertussis (DTaP) vaccine or any of its components was found to contribute to the development of type I diabetes. And, the influenza vaccine does not cause Bell’s palsy or worsen asthma, according to the report.

In 135 of the vaccine-adverse event pairs examined, the committee determined that there was insufficient evidence to accept or reject causation, in most cases because the adverse event occurred extremely rarely or research on its relation to the vaccine reached conflicting results.

The committee did, however, find evidence that the 8 vaccines examined-MMR, varicella zoster, influenza, hepatitis A, hepatitis B, meningococcal, human papillomavirus (HPV), and vaccines with tetanus as a component not in combination with whole-cell pertussis-can cause some adverse effects, particularly in immunodeficient children, but still occur very rarely.

Evidence convincingly supports a causal relationship between the varicella zoster vaccine and disseminated varicella infection; varicella infection with subsequent pneumonia, meningitis, or hepatitis in immunocompromised children; viral reactivation from months to years after the vaccination; and viral reactivation with subsequent meningitis or encephalitis infection.

The MMR vaccine appears to cause benign febrile seizures in infants and young children and, in those with weakened immune systems, is also associated with measles inclusion body encephalitis. Evidence suggests that the MMR vaccine may also cause transient arthralgia in children. Varicella zoster, influenza, hepatitis B, meningococcal, MMR, and tetanus-containing vaccines can trigger anaphylaxis, which can also happen with the HPV vaccine.

Syncope can result from injection with any antigen, according to the report. Because fainting is most likely to occur among adolescents within 15 minutes of vaccine administration, the Centers for Disease Control and Prevention (CDC) advises pediatricians to administer vaccinations to teens when they are seated or lying down and to observe them for 15 minutes after injection. Bursitis can be an injection-related event in any age group.

The CDC recommends 12 vaccines for children, including the 8 vaccines reviewed in the report. The others are rotavirus, inactivated poliovirus, pneumococcal, and haemophilus influenzae type b vaccines.

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