International Notes Measles -- Hungary

Between December 1, 1988, and May 14, 1989, 19,080 measles cases in residents of Hungary were reported to Hungary's National Institute of Hygiene; in the previous 3 years, fewer than 25 cases were reported annually (Figure 1) (1). The overall incidence rate in this epidemic was 186 cases per 100,000 population. Budapest and all 19 counties in Hungary were affected, with county-specific attack rates ranging from 51 to 358 cases per 100,000 population. Six measles-associated deaths occurred (case-fatality rate: 0.03%).

Age data were available for 11,475 reported case-patients. Seventy-five percent of patients were 16-22 years of age. The highest age-specific attack rates (1723 and 1273 per 100,000) occurred in 17- and 18-year-olds, respectively (Figure 2). Attack rates for persons 2-15 years of age ranged from 35 to 165 per 100,000. The attack rate for infants less than 1 year of age was 351 per 100,000.

Preliminary information on vaccine status indicates that an estimated 77% of 17-21-year-olds with measles had previously received live measles vaccine. Based on approximately 93% vaccine coverage, vaccine efficacy for persons in this age group (most of whom were vaccinated from 1969 through 1971) was an estimated 83% (2).

Control measures implemented during the epidemic included mass revaccination of persons 16-22 years of age regardless of previous vaccination history. During February and March 1989, 650,000 doses of vaccine were administered to this target group; reported cases subsequently declined (Figure 3). Reported by: A Vass, MD, Head, Public Health and Epidemiology Div, Ministry of Health and Social Affairs; I Domok, MD, Deputy Director-General, I Straub, MD, Head, Dept of Epidemiology, National Institute of Hygiene, Hungary. Expanded Programme on Immunization, WHO Regional Office for Europe, Copenhagen, Denmark. Div of Environmental Hazards and Health Effects, Center for Environmental Health and Injury Control; Div of Immunization, Center for Prevention Svcs, CDC.

Editorial Note

Editorial Note: In 1969, Hungary began measles vaccination efforts using the live, attenuated Leningrad-16 strain produced in the Soviet Union. From 1969 to 1974, a single dose of vaccine was administered in mass campaigns to persons 9-27 months of age. However, in 1974, mass campaigns were discontinued, and vaccine was administered during routine health care. The recommended age for vaccination was 10 months until 1978, when it was changed to 14 months. Coverage rates of targeted persons during the campaigns ranged from 93% to 99% and have been at least 98% since routine administration began in 1974 (3).

The vaccination program has had a major impact on the epidemiology and annual incidence of measles in Hungary (Figure 1). After vaccination was implemented, the incidence rate decreased until 1973-74, when large epidemics occurred primarily in unvaccinated 6-9-year-olds. The annual incidence rate then decreased until 1980-81, when another epidemic occurred, primarily in 7-10-year-olds. After the epidemic, persons born between 1973 and 1977, who would have received vaccine when the recommended age was 10 months, were revaccinated. Subsequently, the annual incidence rate for measles decreased until 1988 (3,4).

Investigation of this epidemic has prompted concern about the roles of primary vaccine failure (unsuccessful initial vaccination) and secondary vaccine failure (loss of immunity after successful vaccination). The 1988-89 epidemic mainly affected persons 17-21 years of age, who had been targeted to receive vaccine during mass campaigns in the first years of the vaccination program in Hungary. The high agespecific attack rates in this age group, in which vaccine coverage was at least 93%, suggest that vaccine failure played a major role in this epidemic.

Primary vaccine failure may have occurred as a result of poor vaccine handling practices during the early campaigns, vaccination at about 10 months of age when maternal antibody could interfere with successful vaccination, or thermolability of the vaccine used at that time. Secondary vaccine failure has been suspected because persons most affected in this epidemic were vaccinated in the more distant past. Assessing waning immunity may be difficult because virtually all persons 17-21 years of age were vaccinated approximately the same number of years before the epidemic. Few persons 11-16 years of age were single-dose recipients, since they were revaccinated after the 1981 epidemic.

Epidemiologic studies are under way to further assess the epidemic, determine risk factors for vaccine failure, and more accurately determine vaccine efficacy. Data gathered may be of interest to all countries with measles-control programs and elimination goals.

References

1. World Health Organization. Expanded programme on immunization: report of the Meeting of National Programme Managers. Copenhagen: World Health Organization, 1989:14.

2. Orenstein WA, Bernier RH, Hinman AR. Assessing vaccine efficacy in the field: further observations. Epidemiol Rev 1988;10:212-41.

3. World Health Organization. Measles outbreak. Wkly Epidemiol Rec 1989;64:137-8.

4. World Health Organization. Expanded programme on immunization: disease incidence and immunization coverage. Wkly Epidemiol Rec 1983;58:77-80.

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