Encephalitis postvaccinial

The most dreaded complication of smallpox vaccination is postvaccinial encephalitis or encephalomyelitis, which is said to occur even without a cutaneous vaccination reaction (30), although this occurs rarely, if at all (2,31). It is mainly a complication of primary vaccination. There is increased morbidity with increasing age, especially around puberty. It is rare after revaccination. 

Two conditions must be distinguished a histopathological picture characterized by diffuse perivenous focal encephalitis and a condition based on a disturbance of the blood-brain barrier, that is an encephalopathy that characteristically occurs in infants. The incubation period of postvaccinial encephalomyelitis is 9-13 days. Its onset is mostly sudden. The clinical picture varies. Mortality is high (30-50%). Recovery may be complete, but there are often neurological sequelae, such as paresis and extrapyr-amidal disturbances. 

More severe complications of vaccinia vaccination include eczema vaccinatum, progressive vaccinia, and postvaccinial encephalitis. These complications are rare, but occur at least 10 times more often among primary vaccinees than among revaccinees. Eczema vaccinatum is a localized or systemic dissemination of vaccinia virus among persons who have eczema (Figure 27-7). Although usually mild and self-limited, this complication could be severe or even fatal in up to 10% of cases. 

Postvaccinial encephalitis most frequently affects primary vaccinees, with attendant mortality and serious neurologic morbidity of 25%.95 Although the U.S. survey indicated the opposite, most countries reported a greater incidence of postvaccinial encephalitis from primary vaccination of older children and adults than of infants.96... 

---