Prognosis
Mortality rates varied from 30% for variola major to 3% or less for variola minor in unvaccinated people. Malignant (flat-type) and haemorrhagic smallpox were usually fatal.[1]
Immunocompromised people, younger children, and pregnant women had very high mortality rates. Smallpox was noticeably more severe in pregnancy and caused premature termination in up to 75% of women if contracted in the first trimester, and premature delivery in around 60% of women if contracted later in pregnancy. Haemorrhagic smallpox occurred in one quarter of cases of smallpox in pregnant women, and malignant (flat-type) smallpox was twice as common in pregnancy compared with men and non-pregnant women; both were associated with very high mortality. Congenital smallpox occurred but was uncommon.[1]
Acute illness resulted in prolonged immunity to reinfection following recovery. Most studies suggested a longer duration of residual immunity (i.e., at least 20 years) than assumed in smallpox guidelines (which suggested 3-10 years); however, data were limited.[40]
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