W. Katherine Yih, Department of Ambulatory Care and Prevention, Harvard Pilgrim Health Care, 133 Brookline Ave., 6th floor, Boston, MA, USA, Daniel Brooks, Department of Epidemiology, Boston University, Boston, MA, USA, Karen Clements, Massachusetts Department of Public Health, Boston, MA, Susan Lett, Division of Epidemiology & Immunization, Massachusetts Department of Public Health, State Lab Institute, 305 South St, Jamaica Plain, MA, USA, Aisha Jumaan, Child Vaccine Preventable Disease Branch, Epidemiology and Surveillance Division, National Immunization Program, Centers for Disease Control and Prevention, 1600 Clifton Rd, MS E-61, Atlanta, GA, USA, and Jane Seward, Centers for Disease Control and Prevention, National Immunization Program, Chief CVPDB, 1600 Clifton Road, NE, MS E-61, Atlanta, Georgia, USA.
KEYWORDS:
varicella, herpes zoster, chickenpox vaccination, epidemiology, survey methods, BRFSS
BACKGROUND:
Good disease surveillance is essential for assessing the impact of vaccination programs. Starting in 1998, as uptake of varicella vaccine increased, the Massachusetts Department of Public Health enhanced surveillance by including questions in the state-wide Behavioral Risk Factors Surveillance System (MA BRFSS) about the occurrence of varicella and herpes zoster.
OBJECTIVE:
To monitor varicella and herpes zoster epidemiology in Massachusetts in 1998-2000.
METHOD:
Respondents were asked: to enumerate all household members and their ages; whether any household members had chickenpox in the past 12 months and, if so, their age(s); whether any household members had ever had shingles and, if so, their current age(s) and the age(s) when they had shingles. All data were analyzed using the SAS software SURVEYMEANS procedure.
RESULT:
The highest initial incidences of varicella were observed in children 1-4 years of age (83 per 1,000) and 5-9 years of age (76 per 1,000). Varicella incidence declined for all age groups over the 3-year period, by 34% for infants, 86% for 1-4-year-olds, 87% for 5-9-year-olds, 53% for 10-14-year-olds, 83% for 15-19-year-olds, and 82% for adults. We were unable to use data on herpes zoster from 1998. In both 1999 and 2000, herpes zoster incidence increased with age, with no statistically significant difference in total incidence between the two years.
CONCLUSION:
As measured by the MA BRFSS, varicella incidence decreased in all age groups from 1998 to 2000. Any changes in age-specific herpes zoster incidence as a result of mass vaccination could well take a number of years to manifest themselves. A repeat survey is being conducted in 2002; these data will be available in mid-2003. A national survey may be needed to achieve the necessary sample sizes to detect small changes in herpes zoster incidence.
LEARNING OBJECTIVES:
(1) understand recent changes in varicella epidemiology, as measured by the MA BRFSS; (2) understand the potential and limitations of survey methods for detecting changes in incidence of high- and low-prevalence diseases.
See more of Varicella Vaccination Updates and Results of Studies Eight Years into the Vaccination Program
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