The age-dependent risk of postvaccination complications in vaccinees with smallpox vaccine

The use of vaccinia virus in recombinant systems may result in the occurrence of complications observed following smallpox vaccination. The results are presented of a large survey carried out in the USSR between 1968 and 1979. High complication rates are reported, particularly in older primary vaccinees; for example, there were 312.5 cases of neurological complications per million in those aged greater than or equal to 5 years. The author concludes that this factor will limit the use of vaccinia virus in recombinant technology.