Antibody to Varicella-Zoster virus in parturient women and their offspring during the first year of life.

A nursery outbreak of varicella is reported. Serum from 200 parturient women and 131 of their offspring were studied for antibody to varicella-zoster (V-Z) virus to analyze their immunity to varicella. Antibody titers were measured by the sensitive fluorescent antibody to membrane antigen (FAMA) technique. It was found that approximately 5% to 16% of women of child-bearing age in New York City are susceptible to varicella. Women from Puerto Rico or other subtropical and tropical areas are more likely to be susceptible (16%) than others (5%). Infants born to mothers with detectable V-Z FAMA titers almost always had detectable V-Z antibody at birth. In serial serum specimens obtained from 67 initially seropositive babies during the first year of life, it was found that by 6 months of age most infants were no longer passively protected against varicella. These observations may explain why varicella is not uncommonly observed in young babies.