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HIB
POST 00945E : MATERIAL OF INTEREST 24 June 2006
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You will find below, first a slightly modified message from Robert Davis
(mailto:[email protected]) from UNICEF/ESARO drawing our attention to the
revised WHO guidelines on vaccination coverage surveys published in 2005,
recently circulated through Tech Updates. I repeat his appeal for people
with experience with the revised methodology to share this experience and
their comments.
Then two abstracts with links to information on the site of Dev-Zone, a
non-governmental resource center from Aotearoa New Zealand, on
international development and global issues, that some of you may know
already. The first is an interview with Salil Shetty, director of the U.N.
Millennium Campaign. The second, nicely constructed, provides information
on 17 success cases, including smallpox, polio, measles and TB.
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NATIONAL VACCINATION COVERAGE SURVEYS WITH ENHANCED PRECISION
Since its creation in 1974, the Expanded Programme on Immunization has
relied for coverage evaluation on the 30 cluster survey, with 7 infants
sampled in each cluster for maternal TT coverage and 7 one-year-olds for
child vaccination coverage. Coverage is calculated, within broad confidence
intervals, based on card alone and card plus history (1). The scanty
literature on maternal recall of child vaccination status suggests that it
is generally reliable, even among illiterate populations (2).
The difficulty with the 30 x 7 method comes when a government, for example,
decides to compare coverage among individual states, provinces or regions.
If Provinces A and B register 55 and 60 percent respectively, one can say
with some confidence that Province A has a true value between 45 and 65
percent, while Province B has a true value between 50 and 70 percent.
Although these confidence intervals of 10 percentage points narrow
somewhat as coverage approaches the extremes of 0 and 100 percent, they are
not very satisfactory for most programmes trying to rank order their
provinces in ascending order of coverage.
For this reason, the World Health Organization and partners have developed
a modification to the classic 30 x 7 coverage survey. Its practical
application calls for slightly larger numbers of clusters. For
example,whereas the 11 regions of Ethiopia would have required 330 clusters
in the classical methodology, 467 clusters were needed under the new
methodology to do the national coverage survey just completed.
The survey modifications are based on revised WHO guidelines published in
2005. The heart of the modification is set down in Table C, pages 55ff of
the document, "Number of children per cluster if desired precision is 5%."
The WHO document is directly available (820K) at :
http://www.who.int/vaccines-documents/DocsPDF05/www767.pdf
This greater precision incurs additional costs in terms of survey costs.
But those additional costs still permitted Ethiopia to budget its 2006
surveys for $149,000, a tiny fraction of the >$30 million used on EPI in
that country last year for routine EPI and mass campaigns.
Other distinctive features of the current Ethiopian survey include the
following:
o Establishment of the survey Core Group (or Steering Committee) to advise
and oversee the implementation of the survey;
o In some regions (e.g. Southern Nations) the number of clusters and
children/women per cluster was also increased to enhance precision,
bringing it below 5%;
o Assignment of one supervisor per one team to ensure close monitoring of
field activities and high quality of data collected;
o To enhance confidence and objectivity of the survey, the supervisors and
most of the interviewers were interchanged between neighbouring zones.
Do any readers from other countries have experiences with use of the
revised methodology?
Bob Davis
1 R. H. Henderson and T. Sundaresan, "Cluster Sampling to Assess
Immunization Coverage: A Review of Experience with a Simplified Sampling
Method," Bull World Health Organ, 1982: 60(2): 253-60.
2 E. T. Gareaballah and B. P. Loevinsohn, "The Accuracy of Mother's
Reports about their Children's Vaccination Status" Bull World Health
Organ, 1989; 67(6), 669-674.
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NINE YEARS, EIGHT GOALS, NO TIME TO WASTE
Salil Shetty is the director of the U.N. Millennium Campaign to help
achieve the Millennium Development Goals. With less than a decade to go
before the deadline to achieve these development targets, in this interview
he speaks about the current status of the MDGs. (Mithre J. Sandrasagra, IPS
NEws, 12 June 2006).
http://www.dev-zone.org/cgi-bin/links/jump.cgi?id=10711
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MILLIONS SAVED : PROVEN SUCCESSES IN GLOBAL HEALTH
One of the greatest human accomplishments has been the spectacular
improvement in health since 1950. This site looks at success: 17 cases in
which large-scale efforts to improve health in developing countries have
succeeded - saving millions of lives and preserving the livelihoods and
social fabric of entire communities.
Eradicating smallpox worldwide.
Preventing HIV and sexually transmitted infections in Thailand.
Controlling tuberculosis in China.
Eliminating polio in Latin America and the Caribbean.
Saving mothers' lives in Sri Lanka.
Controlling onchocerciasis in sub-Saharan Africa.
Preventing diarrheal deaths in Egypt.
Improving the health of the poor in Mexico.
Controlling trachoma in Morocco.
Reducing guinea worm in Asia and sub-Saharan Africa.
Controlling Chagas disease in the southern cone of South America.
Reducing fertility in Bangladesh.
Curbing tobacco use in Poland.
Preventing iodine deficiency disease in China.
Eliminating measles in southern Africa.
Preventing dental caries in Jamaica.
Preventing Hib disease in Chile and The Gambia.
Learn about what made these efforts so successful. (Ruth Levine, Centre for
Global Development, 2006)
http://www.dev-zone.org/cgi-bin/links/jump.cgi?ID=10732
Those who would be interested in broader information and general knowledge,
please visit the Dev-Zone site at :
http://www.dev-zone.org/knowledge/
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