Measles vaccine failure and infections.

Abstract

To The Editors: We previously reported that respiratory infections and diarrhea after vaccination for measles hampered antibody responses in 9-month-old Thai children vaccinated in 21 weekly sessions during the rainy season in 1995.1 All but one of the children in the study (a seroconverter) were afebrile when vaccinated, but nearly one-half had rhinorrhea. Nine of the children failed to mount an antibody response by 5 weeks after vaccination and were considered vaccine failures. The symptom densities of both respiratory and diarrheal illnesses during the 2 weeks after vaccination were significantly more common in vaccine failures than seroconverters. Paired sets of sera were tested for evidence of infection with respiratory syncytial viruses (RSV) and rotaviruses. Overall 4 of the 9 (44%) children with vaccine failure had a significant rise in specific IgG to RSV, compared with only 3 of 92 (3%) seroconverters (P = 0.0009, by Fisher's test). Each of the 4 had rhinorrhea and cough during follow-up, but only 2 had rhinorrhea when vaccinated. Two of 7 attending one of the vaccination sessions were infected; otherwise no clustering was noted. Two (22%) of the 9 vaccine failures and 18 (20%) of the seroconverters had serologic evidence of rotavirus infections. The 2 children who were vaccine failures and positive for rotavirus also had concurrent evidence of RSV infection, and one of them also had a diarrheal illness during follow-up. There was no significant overall association between diarrhea and rotavirus infection, indicating that many of the infections may not have occurred during the 2-week follow-up. Clustering of infections was noted by vaccine session; 3 of 6, 3 of 5 and 3 of 6 children attending 3 different sessions were infected, suggesting the possibility of clinic acquisition. Only a few2, 3 of many studies have reported a relationship between infections and response to measles vaccination. Variation in the prevalence of RSV infections from place to place and season to season may be one factor underlying observed differences. Because we cannot predict whether a well or mildly ill child will have an infection that impairs response after vaccination, children with mild illnesses should continue to be vaccinated. However, infections occurring at and postvaccination may underlie the reduced efficacy of measles vaccination in 9-month-old infants in developing countries, may be institutionally acquired more commonly than generally appreciated and may adversely affect antibody responses during national measles vaccination campaigns conducted during the respiratory disease season. John Bennett, M.D. Dean Erdman, Ph.D. Roger Glass, M.D. William Bellini, Ph.D. Janet Heath, M.S. Sriluck Simasathien, M.D. Sricharoen Migasena, M.D. Department of Epidemiology; Rollins School of Public Health; Emory University (JB) Viral and Rickettsial Disease Division; National Center for Infectious Diseases; CDC; Atlanta, GA (DE, RG, WB, JH) Pramongkutklao Hospital; Vaccine Trial Centre; Mahidol University; Bangkok, Thailand (SS, SM)