Postvaccination Adverse Events

Based on background rates, they determined that within 6 weeks of vaccination there would be 21.5 coincident cases of GBS per 10 million vaccine recipients, and 86.3 cases of optic neuritis per 10 million female vaccinees. Spontaneous abortions would occur in 16,684 of every 1 million vaccinated pregnant women, and sudden death within 1 hour of any symptom onset in 5.75 of every 10 million people vaccinated (Lancet 2009;374:2115-22).

Another important analysis was conducted by the CDC to determine whether 33 reported cases of GBS in 11- to 19-year-olds within 42 days of receipt of meningococcal conjugate vaccine were causally linked. Background data from the 2000–2004 Healthcare Cost and Utilization project estimated that there would be very close to 36 cases for the entire age cohort, suggesting there was no causal link. However, just 20 cases would be expected among 15- to 19-year-olds, but the actual number was 26.

Although not statistically significant, this difference was enough to merit continued monitoring by the CDC, which advised that children with prior GBS not receive the vaccine (MMWR 2006;55:364-6).

Finally, a population-based case-control study from France investigated cases of acute disseminated encephalomyelitis, optic neuritis, and transverse myelitis in children younger than 16 years of age between 1994 and 2003, using 12 controls per case matched for age, sex, and geographic location. Rates of hepatitis B vaccination were 24% in cases and 27% in controls, for an adjusted odds ratio of 0.74 (Neurology 2009;73:1426-7). One might conclude from this that hepatitis B vaccine is actually protective, but the result was not statistically significant.