An important safety issue related to the varicella vaccine is the impact on the epidemiology of herpes zoster both in vaccinees as well as in individuals previously infected with wild-type varicella.
Current data are insufficient to define the incidence of adverse events in primary vaccinees as opposed to individuals re-vaccinated after a long interval.
Consistent adverse effects reported in smallpox vaccinees have been myopericarditis and dilated cardiomyopathy; the frequency of each adverse effect exceeds what might have occurred by coincidence.