Pneumonia, which may be caused by varicella or secondary bacterial infection, is another potentially serious complication. Maternal varicella during the first half of pregnancy poses a small but measurable risk to the fetus in that it may result in congenital varicella syndrome. In addition, the risk of fatal maternal infection appears to be increased, particularly late in pregnancy. Immunocompromised children and adults are at increased risk for complications of both varicella and zoster. Fortunately, antibody prophylaxis and acyclovir therapy have brought a substantial reduction in mortality in this group.
Healthy adults are much more likely than healthy children to have complications of varicella.
They are at increased risk for pneumonia and central nervous system complications. In addition, the rate of hospitalization for adults is four times that for children. Only about 1 in 20 cases of varicella occur after age 20, but all complications, including one third of deaths, are disproportionately represented in this age-group. Death from varicella is uncommon but is an important factor in calculating immunization strategy. At least once every 5 days, an American child or adult dies of varicella.