Increased incidence of herpes zoster in normal children infected with varicella zoster virus during infancy: community-based follow-up study.

We surveyed outbreaks of varicella zoster virus (VZV) and herpes zoster virus, involving 31 outbreaks of chicken pox, in a semiclosed institution in Osaka Japan during the 34 years between 1949 and 1984. Eight hundred forty-nine infants and children who had had clinical varicella during the first 4 years of life and those who had resided in the institution at least 12 to 144 months after the onset of varicella were included in the study. Nine cases of zoster were observed among children who had acquired varicella during the first year of life, but there was no case of zoster in those who had acquired varicella after 1 year of age. In 61,800 person-months of observation, the overall incidence rate of zoster was calculated as 0.15 per 1000 person-months for the population at risk. The incidence rate in children infected with VZV when younger than 2 months was 1.0 per 1000 person-months during the first decade of life. This rate was significantly (P less than 0.005) greater than that (0.19 per 1000 person-months) in children who had varicella when they were 2 to 11 months of age. These observations suggest that zoster occurs at a significantly shorter interval if VZV infection is acquired during infancy. More than 85% of subjects with prior infection were intimately reexposed to epidemic varicella during their residency in the institution, before having zoster. Epidemic reexposure to varicella during follow-up resulted in enhancement of preexisting immunologic reactivity, but did not prevent subsequent zoster in the population studied.

Seroepidemiologic behavior of varicella zoster virus infection in a semiclosed community after introduction of VZV vaccine.

A survey of varicella and measles has been made in a semiclosed institution housing infants and children in Osaka since 1950. Live measles and varicella vaccines were introduced into the institution in 1974 and 1975, respectively. Nine of 10 measles outbreaks occurred during the 24 years before use of measles vaccine, and only one occurred during the 9 years after introduction of measles vaccine. In contrast, the incidence of varicella outbreaks has not been reduced after introduction of varicella vaccine, although the rate of immune individuals in the population against varicella has been kept at 74.2% for the 8 years since 1975, which was higher than that against measles (65.8%) during the same period. All successfully vaccinated children, however, were resistant to clinical varicella, and the number of clinical cases has been markedly reduced. Using the fluorescent antibody to membrane antigen and varicella zoster virus skin testing, the kinetics of secretory, humoral, and cellular immune responses to VZV was examined in vaccinated and naturally infected subjects and found to be comparable in both groups during repeated exposure to varicella epidemics. These results suggest that the seroepidemiologic behavior of varicella would not be significantly altered after introduction of varicella vaccine, in contrast to that of measles since general use of measles vaccine.

Immunologic and epidemiologic aspects of varicella infection acquired during infancy and early childhood.

The development of varicella zoster infection was studied in a population of infants under one year of age during three outbreaks of varicella in a semi-closed domiciliary institution for infants in Japan. Over a period of four years, many residents ranging in age from 27 days to 32 months were tested for cutaneous reactivity to VZV antigen, and VZV-specific antibody activity before, during, and after each outbreak of varicella. Of these, 85 subjects developed clinical varicella, with an overall attack rate of 100% for all susceptible subjects. All the infants under 2 months of age were infected following such exposure, despite the presence of pre-existing maternal antibody. The degree of cutaneous involvement appeared to be milder (less than 20 vesicles) in infants less than 2 months of age, and severe cutaneous disease (with over 300 eruptions or confluent rash) occurred more frequently in subjects 2 to 11 months of age. Pre-existing antibody did not prevent development of illness, or alter the degree of antibody or cellular immune response to subsequent infection. However, the peak cutaneous reactivity to VZV antigen after infection was found to be significantly lower in infants under 2 months of age.