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MEASLES OUTBREAKS: THREE LESSONS FROM THREE COUNTRIES -- NOSOCOMIAL TRANSMISSION A FACTOR IN OUTBREAKS

Monday, 7th of September 2009 Print

MEASLES OUTBREAKS: THREE LESSONS FROM THREE COUNTRIES
 
From South Africa, we learn that failure to vaccinate was the main driver  in their recent outbreak, though vaccine take rates were somewhat lower in  HIV seropositives.
 
 From Bulgaria, we learn the need to vaccinate all ethnic groups,  including, in Bulgaria, the Roma.
 
 From Taiwan, we learn about the importance, in some settings, of nosocomial  transmission.
 
 Good reading.
 
 BD
  
 SOUTH AFRICA
 
 Students of measles will know that South Africa, with a large and
 self-financed health service, had a measles outbreak from 2003 to 2005. In
 this article, McMorrow and colleagues look at the reasons for this
 persistent transmission. As in so many investigations, it was failure to
 vaccinate, rather than vaccination failure, that was the main driver of the
 outbreak. In particular, the authors do not see lower measles
 seroconversion among HIV seropositives as a main driver of the outbreak.
 This is an important conclusion for southern Africa, where high vaccination
 coverage is in many countries associated with high HIV seroprevalence.
 (Abstract at foot of this E-mail).
 
 BULGARIA
 
 Writing in Eurosurveillance, at
 http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=19259
 Marinova and colleagues analyze the current measles outbreak in their
 country.
 
 'Despite the high national immunisation coverage with MMR vaccine, the
 current measles outbreak clearly demonstrates the existence of pockets of
 non-immunised population, here specifically the Roma population. A quick
 risk assessment made by the epidemiologists investigating the outbreak
 concluded that the minority groups and living in closed communities as
 described above are at higher risk of measles infection and should be
 offered a supplementary measles immunisation.'
 
 TAIWAN, CHINA
 
 This report by Chen and colleagues, available at
 ajws.elsevier.com/ajws_archive/200941084A6066.pdf
 shows that 17 of the 22 cases investigated were infected by nosocomial
 transmission.  'Despite  95% MMR coverage,outbreaks can still occur.
 Recent nosocomial outbreaks illustrated the high transmissibility of
 measles, the importance of adherence to the routine vaccination schedule
 for children and proper vaccination before traveling aboard.'
 
 
 Good reading.
 
 BD
 
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 | [ ] |
 |------|1: S Afr Med J. 2009 May;99(5):314-9.
 Measles outbreak in South Africa, 2003-2005.
 McMorrow ML, Gebremedhin G, van den Heever J, Kezaala R, Harris BN,
 Nandy R, Strebel P, Jack A, Cairns KL.
 Malaria Branch Division of Parasitic Diseases, National Center for
 Zoonotic, Vector-Borne, and Enteric Diseases, Centers for Disease
 Control and Prevention and United States Public Health Service,
 Atlanta, USA. MMcmorrow@cdc.gov
 OBJECTIVES: Measles was virtually eliminated in South Africa
 following control activities in 1996/7. However, from July 2003 to
 November 2005, 1676 laboratory-confirmed measles cases were
 reported in South Africa. We investigated the outbreak's cause and
 the role of HIV.
 DESIGN: We traced laboratory-confirmed case-patients residing in
 the Johannesburg metropolitan (JBM) and O. R. Tambo districts. We
 interviewed laboratory--or epidemiologically confirmed
 case-patients or their caregivers to determine vaccination status
 and, in JBM, HIV status. We calculated vaccine effectiveness using
 the screening method.
 SETTING: Household survey in JBM and O. R. Tambo districts. Outcome
 measures. Vaccine effectiveness, case-fatality rate, and
 hospitalisations.
 RESULTS: In JBM, 109 case-patients were investigated. Of the 57
 case-patients eligible for immunisation, 27 (47.4%) were
 vaccinated. Fourteen (12.8%) case-patients were HIV infected, 46
 (42.2%) were HIV uninfected, and 49 (45.0%) had unknown HIV status.
 Among children aged 12-59 months, vaccine effectiveness was 85%
 (95% confidence interval (CI): 63, 94) for all children, 63% for
 HIV infected, 75% for HIV uninfected, and 96% for children with
 unknown HIV status. (Confidence intervals were not calculated for
 sub-groups owing to small sample size.) In O. R. Tambo district,
 157 case-patients were investigated. Among the 138 case-patients
 eligible for immunisation, 41 (29.7%) were vaccinated. Vaccine
 effectiveness was 89% (95% CI 77, 95).
 CONCLUSIONS: The outbreak's primary cause was failure to vaccinate
 enough of the population to prevent endemic measles transmission.
 Although vaccine effectiveness might have been lower in
 HIV-infected than in uninfected children, population vaccine
 effectiveness remained high.

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