Measles outbreaks in Micronesia, 1991 to 1994.

BACKGROUND: Several islands in Micronesia experienced large measles outbreaks, during 1991 through 1994. Except for Guam, none of the islands had reported measles outbreaks during the previous 20 years. METHODS: To characterize the outbreaks, measles surveillance data, hospital records and death certificates were reviewed. Preoutbreak vaccination coverage rates were assessed by reviewing public health vaccination records. Viral isolates were genetically sequenced to determine the source of transmission. Linear regression analysis was performed to assess the effectiveness of outbreak control measures. RESULTS: Between 1991 and 1994 more than 1300 measles cases and 16 measles-related deaths were reported in Micronesia. Preoutbreak vaccination coverage rates among 2-year-old children were 55 to 94%. Genetic sequencing of the viral isolates and epidemiologic investigations suggested transmission between islands and new importations from outside of Micronesia. The highest attack rates were among children ages < 5 years (20/1000) and 10 to 19 years (38/1000). Compared with attack rates among children ages < 1 and 10 to 19 years, attack rates were lower among those ages 5 to 9 years, in whom 2-dose vaccination coverage rates were highest (P < 0.001). Early and rapid implementation of mass vaccination campaigns was significantly associated with shorter duration of outbreaks (P = 0.049). CONCLUSION: The measles outbreaks in Micronesia show that island populations may be highly susceptible to measles. High two-dose vaccination coverage levels must be maintained to prevent such outbreaks. Early and rapidly implemented mass measles vaccination campaigns were effective in control of island outbreaks. Strengthening public health infrastructure and surveillance is necessary for early identification of outbreaks and rapid implementation of mass campaigns.

The hepatitis B immunization campaign for children in the Federated States of Micronesia.

Hepatitis B has long been recognized as hyperendemic among persons residing in the western Pacific. Effective control strategies have not been described. From December 1988 through October 1989, the Federated States of Micronesia (FSM) conducted a campaign to immunize children through age 6 years with three doses of hepatitis B (HB) vaccine. In addition, HB vaccination was incorporated into the routine immunization schedule for all children born in FSM, with the first dose given to newborns. Between December 1988 and October 1989, a total of 64,085 doses of HB vaccine were administered to the children. After the start of the campaign, the subject group was enlarged to include children through 15 years of age in the States of Yap and Kosrae. Fifty-nine percent of the enlarged group in all States received a complete series of HB vaccinations. During each client encounter, individual immunization records were examined and diphtheria-pertussis-tetanus, oral polio vaccine, and measles-mumps-rubella antigens were administered to children who were not adequately immunized. The annual immunization assessment for 1990 showed coverage improved significantly from previous years in every FSM State.