title: MMR vaccine effectiveness in an outbreak that involved day-care and primary schools.
abstract: OBJECTIVE
  In 2006, a large measles outbreak occurred in Catalonia (Spain), where the immunization schedule included two doses of MMR vaccine at 15 months and 4 years. The aim of this study was to investigate the vaccine effectiveness (VE) of MMR in children attending day-care and pre-school centres and to estimate the number of cases that would have been avoided by administering the first dose of MMR at 12 months.
  
  
  METHODS
  A retrospective cohort study was carried out between October 2006 and January 2007 in day-care and pre-school centres with confirmed measles cases. VE was calculated in children aged ≥15 months without previous measles infection. Cases avoided by advancing the first dose of MMR to 12 months were estimated by calculating the basic and effective reproduction number in centres where transmission outside the class was observed.
  
  
  RESULTS
  Fifteen centres and 1394 children were included. There were 77 confirmed cases (attack rate=5.5%). Vaccination coverage of the 1121 children aged ≥15 months was 91.6% and VE was 96% (95%CI 89-98%). There were 33 (41%) cases in the 81 children aged 12-14 months. Advancing the first dose to 12 months would have prevented 74 cases (91.5%) and lowered the attack rate from 41% to 8.6%.
  
  
  CONCLUSIONS
  Over 90% of cases in children aged 12-14 months would have been avoided by MMR administration at 12 rather than 15 months. We strongly recommend advancing the first dose of MMR to 12 months in order to reduce the risk of measles outbreaks.
authors: Epidemiological Surveillance Unit of Barcelona-Zona Sud. Department of Health, Generalitat of Catalonia, Barcelona, Spain. ibarrabeig@catsalut.cat
authors: Irene
authors: I
authors: Barrabeig
authors: Ariadna
authors: A
authors: Rovira
authors: Pilar
authors: P
authors: Muñoz
authors: Joan
authors: J
authors: Batalla
authors: Cristina
authors: C
authors: Rius
authors: Josep Anton
authors: JA
authors: Sánchez
authors: Àngela
authors: À
authors: Domínguez
mesh_terms: D050936:Basic Reproduction Number; D002648:Child; D002656:Child Day Care Centers; D002675:Child, Preschool; D015331:Cohort Studies; D004196:Disease Outbreaks; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008457:Measles / Q000453:epidemiology* / Q000517:prevention & control* / Q000635:transmission; D022542:Measles-Mumps-Rubella Vaccine / Q000008:administration & dosage* / Q000276:immunology*; D012189:Retrospective Studies; D012574:Schools; D013030:Spain / Q000453:epidemiology
chemical_list: D022542:Measles-Mumps-Rubella Vaccine