Monday, 7th of September 2009 |
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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www.measlesinitiative.org www.technet21.org www.polioeradication.org www.globalhealthlearning.org www.who.int/bulletin allianceformalariaprevention.com www.malariaworld.org http://www.panafrican-med-journal.com/ |