These incompletely vaccinated children and adolescents received only the first dose, at the age despite of one year, and missed or refused the second dose. Based on the vaccination registrations found in ��Vaccinnet�� 49% were unvaccinated and 17% were incompletely vaccinated. A total of 30 pupils claimed within the questionnaire to have been previously infected with measles virus. In about one third of the questionnaires the reason for not vaccinating their child was described by the parents as ��a personal choice��. Laboratory testing The National Reference Center for Measles and Rubella analysed a total of 45 oral fluid samples from suspected measles cases during the outbreak in Ghent. The total number of positive samples at the reference center was 29.
Samples from two infants were not tested at the reference center but were found measles IgM positive at another laboratory. The total number of laboratory confirmed cases was 31. We obtained samples from 13 of the 14 children in the day care center, 3 serum samples and 10 saliva samples. Two serum samples were only tested for measles IgM and both were measles IgM positive. Five, of which one serum sample, were found positive for both measles IgG and IgM. In the remaining six saliva samples no measles IgM could be found but all were positive for measles IgG. PCR genotyping of two oral fluid samples resulted in genotype D4-Hamburg for both. Aside from the day care center, 34 samples were collected, 18 were positive for measles. Five of these samples had both measles RNA and measles IgM, four were only measles IgM positive and in nine only measles RNA could be detected, no measles antibodies.
The 16 samples in which measles RNA was detected were also genotyped by an in-house developed assay. All were genotyped as D4, subvariant strain MVs/Ghent. BEL/09.11/1/[D4]. This strain was clearly related to MVs/Hamburg.DEU/03.09/ [D4]. Measures taken Several control measures were taken to limit the spread of measles. We tried to reduce the number of susceptibles by means of an immunization campaign in the schools. Prior to the campaign all students were given a leaflet with the risks and complications of a measles infection and some information on vaccination. Children with incomplete measles vaccination were offered vaccination at the school, during school hours, by the outbreak team.
During the vaccination campaigns on 21, 22 and 23 March 2011, we vaccinated 25% (N=79) of 321 incompletely vaccinated or unvaccinated children. We raised clinical alertness by informing health care professionals on the outbreak. Several letters and e-mails were sent to emergency departments, GPs and pediatricians. GSK-3 Physicians were made aware of the procedures to obtain free test kits for oral fluid sampling. We tried to isolate cases from unimmunized persons.