Measles Epidemic in Romania, 1996-1998; Assessment of Vaccine Effectiveness by Case-Control and Cohort Studies

Abstract

A measles epidemic occurred in Romania with 32,915 cases and 21 deaths reported between November 1996 and June 1998, despite high vaccination coverage since the early 1980s. Most cases were unvaccinated children aged <2 years and vaccinated school-aged children. A case-control study among preschool children and a cohort study among primary-school children were conducted to estimate effectiveness of Romanian-produced measles vaccine, and to evaluate age at vaccination and waning immunity as risk factors for vaccine failure. Both studies indicated that measles vaccine was highly effective. One dose reduced the risk for measles by 89% (95% confidence interval (CI) 85, 91); two doses reduced the risk by 96% (95% CI 92, 98). Children vaccinated at <1 year of age were not at increased risk for measles compared with children vaccinated at > or =1 year. Waning immunity was not identified as a risk factor since vaccine effectiveness was similar for children vaccinated 6-8, 9-11, and 12-14 years in the past. Because specific groups were not at risk for vaccine failure, an immunization campaign that targets all school-aged children who lack two doses may be an effective strategy for preventing outbreaks. A mass campaign followed by increased first-dose coverage should provide the population immunity required to interrupt indigenous measles virus transmission in Romania.

Morbidity and Mortality from Measles in Cameroonian Children: Implications for Measles Control

“…According to Nokles et al [20], it is not beneficial to simply reduce the vaccination age. A two doses of measles vaccination policy is more efficient for measles control than the one dose currently administered [13,[21][22][23][28][29][30], but budgetary constraints constitute a serious barrier for the implementation of this strategy. Besides, a multidose program may distract the delivery of the routine vaccine at 9 months to the most vulnerable children [24].…”

“…Waning immunity is not a risk factor of measles [29], but rather the effectiveness of the measles vaccine. In Cameroon, vaccines may be delivered under suboptimal conditions, and this might have increased the susceptibility of infants to measles.…”

Measles elimination: a mass immunization campaign in Romania

“…1 Vaccine effectiveness studies conducted during the epidemic found the measles vaccine to be highly effective, indicating that measles among vaccinated schoolaged children was primarily due to failure to respond to a single dose of measles vaccine. 2 A nationwide campaign was conducted to immunize school-aged children, most of whom were not immunized under the second-dose policy established in 1994 (persons aged 10-18 years). This campaign appears to have reduced susceptibility to levels required to prevent further measles outbreaks and interrupt the transmission of indigenous measles.…”

“…2 Social mobilization at national, district, and community levels was largely conducted by the Romanian Red Cross. Close collaboration and coordination with the Ministry of Health and district health departments was essential for sending clear and timely messages to the public.…”

Measles eradication: is it in our future?

“…Further, attack rates for measles, even 10 or more years after vaccination, tend to be 5% or less, consistent with known primary vaccine failure rates. 57,58 While waning immunity may occur, it does not appear to be a major impediment to measles elimination in the countries in which it has been carefully evaluated. 53,54,57,58 Vaccinees exposed to natural measles may develop subclinical infections manifested by boosts in antibody titers.…”