Earlier this year, an outbreak of measles was detected in Bulgaria, following an eight-year period without indigenous measles transmission, and continues to spread in the country. By the end of 48 week of 2009 (first week of November), 957 measles cases had been recorded. Most cases are identified among the Roma community living in the north-eastern part of the country. Measles has affected infants, children and young adults. The vaccination campaign that started earlier in the year in the affected administrative regions continues, targeting all individuals from 13 months to 30 years of age who have not received the complete two-dose regimen of the combined measles-mumps-rubella (MMR) vaccination.
Comment In: Euro Surveill. 2009;14(50). pii: 1944920070940
The benefits of vaccination are, in general, recognized. For some diseases these benefits are obvious. When starting or evaluating new vaccination programmes, a more critical approach is needed. Before starting vaccination against measles and rubella in Finland a cost-benefit study was performed. According to those studies the net benefits of each vaccination would be ca. 100 million Finnish marks in 25-30 years. Those benefits not measurable in money value of human life, decrease of suffering, etc., were not included. For the purpose of formulating the national influenza vaccination policy a similar study was performed on influenza. The method used before seemed to be less suitable, however, with certain assumptions the vaccinations against influenza proved to be profitable.
Anamnestic data in respect to measles failed to correspond to the results of serological examination of contacts at the foci of the given infection. The collective immunity level in children's institutions is inadequate for the prevention of measles outbreaks. The incidence of the disease depended both on the level of immunity among the children and on the duration of presence of the source of infection in the focus. Live measles vaccine protected 90 percent of the vaccinated children from contracting the disease in the foci. At the very beginning of the postvaccinal period immunization defects were revealed in 26.5 percent of the vaccinated children who fell ill with measles. Morbidity index among the vaccinated individuals constituted 3.8 percent. One of the causes of measles contraction by the vaccinated individuals was the loss of postvaccinal immunity. Systematic control over the antimeasles immunity level with the aid of serological investigations is necessary for the purpose of detection of persons sensitive to measles in children's collective bodies.
In the 1970s, mass vaccination projects were started in various parts of the world against measles and congenital rubella, with eradication as the final goal. In many developing and industrial countries, including Finland, the elimination of measles failed because of low vaccination coverage. In Finland, a combined measles, mumps, and rubella (Virivac) vaccination program was started in 1982. Computerized recording of the vaccinated children was considered necessary and was integrated with the population registry to identify the hard-to-reach families. Several interventions improved compliance: a mass media campaign and notification of nonvaccinated children to local health professionals and parents. All successive campaigns increased vaccination coverage significantly, with the notification of parents about their nonvaccinated child being especially effective. A vaccination coverage of over 96% was achieved, which theoretically prevents measles, mumps, and rubella transmission.
Despite a population immunity level estimated at approximately 95%, an outbreak of measles responsible for 94 cases occurred in Quebec, Canada. Unlike previous outbreaks in which most unvaccinated children belonged to a single community, this outbreak had cases coming from several unrelated networks of unvaccinated persons dispersed in the population. No epidemiological link was found for about one-third of laboratory-confirmed cases. This outbreak demonstrated that minimal changes in the level of aggregation of unvaccinated individuals can lead to sustained transmission in highly vaccinated populations. Mathematical work is needed regarding the level of aggregation of unvaccinated individuals that would jeopardize elimination.
In Poland 120 measles cases were registered in 2006 (0.31 per 100,000 population). It was a substantial increase, compared to the years 2002-2005, when the number of locally-acquired cases was inferior to 1 case per 1 000 000 inhabitants. Three cases were linked to a large Ukrainian outbreak, including the 2006 index case on the Polish territory. Out of 106 cases with vaccination history available, 62 (58%) were not vaccinated, 26 (25%) were fully vaccinated (including 16 laboratory confirmed), and 18 (17%)--incompletely vaccinated. The most affected age groups were children under 2 years of age (incidence 2.62 per 100,000 population), 5-year olds (1.08), and adults aged 25-29 years (1.09). In 20 cases complications were seen, including pneumonia (n = 10) and otitis media (n = 6). 75 measles cases (63%) were hospitalized, no deaths were recorded. The 2006 outbreak lead to a substantial improvement of measles surveillance performance. Two hundred eighty-nine suspect cases were reported, of which 252 (89%) were tested serologically for measles. Additionally, molecular testing of suspect cases was introduced in 2006. The first isolated virus strains belong to the D4 and D5 genotypes, not related to the Ukrainian outbreak. In order to properly document measles elimination during following year, high sensitivity of rash-like illness surveillance should be maintained, and isolation of viral strains from each chain of infection should be attempted.