Journal article
Reply to comments on Monitoring vaccination coverage: Defining the role of surveys.
Dear Editor,
We thank Pond and Mounier-Jack for their comments on our
paper, ‘‘Monitoring vaccination coverage: Defining the role of
surveys” [1]. We agree that for many countries, administrative
estimates of coverage are greatly inflated and misleading for programme
planning purposes. The robustness of the WHO-UNICEF
estimates of national immunization coverage (WUENIC) depends
on the quality of the underlying data reviewed, which include
administrative reports, as well as probability and non-probability
sample surveys. In 2012, the Grade of Confidence (GoC) was introduced
as a means of conveying uncertainty in WUENIC [2] and is
low in the seven conflict-affected countries listed by Pond and
Mounier-Jack. Table 1 shows that in five of these countries,
vaccination cards were available for less than half the children surveyed;
when card availability is low, it is particularly difficult to
compare coverage trends. For example, in Nigeria, the proportion
of children with DTP3 according to card was similar in surveys in
2010, 2011 and 2013, but in the EPI survey of 2010 a verbal history
of vaccination was reported for 43% of children, more than double
that of previous or subsequent surveys. Elsewhere, results from
surveys did not always match expected trends (e.g. no apparent
fall in coverage between surveys despite a 7 month stockout of
DTP in one country), and some results were very unlikely (e.g. zero
dropout between DTP1 and DTP3 in one Multiple Indicator Cluster
Survey (MICS) (data from country reports at http://apps.who.int/
immunization_monitoring/globalsummary/wucoveragecountrylist.
html)).
The updated WHO guidelines on vaccination coverage surveys
(http://www.who.int/immunization/monitoring_surveillance/
Vaccination_coverage_cluster_survey_with_annexes.pdf) discuss the challenges of using a new survey to compare with an older
one, particularly an immunization coverage survey – these often
lacked information on likely biases and confidence intervals were
either not reported or not very meaningful from non-probability
samples. The best way to compare results from different surveys
is to plan a pair of surveys for such a purpose and work very hard
to ensure standardised, well-documented and high quality data
collection in both. Pond and Mounier-Jack suggest that two such
surveys are feasible within each 5 years period. We would be
reluctant to stipulate any particular interval as the usefulness of
repeat surveys will depend in part on the likelihood of a change
in coverage having occurred (which can be predicted from
monitoring other indicators) [1] and the availability of accurate
documentation of vaccination status on home-based or clinic
records. Most of all, surveys should lead to action to strengthen
programme performance and this is likely the weakest link in
many countries, including those affected by conflict.
Languages
- English
Journal
Vaccine
Volume
2016 Dec 7;34(50):6112-6113. doi: 10.1016/j.vaccine.2016.09.067.
Type
Journal article
Categories
- Data
Topic references
COV-METH-PUB