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Clustered lot quality assurance sampling: a tool to monitor immunization coverage rapidly during a national yellow fever and polio vaccination campaign in Cameroon, May 2009

  • L. PEZZOLI (a1), R. TCHIO (a2), A. D. DZOSSA (a3), S. NDJOMO (a3), A. TAKEU (a3), B. ANYA (a4), J. TICHA (a4), O. RONVEAUX (a5) and R. F. LEWIS (a6)...

We used the clustered lot quality assurance sampling (clustered-LQAS) technique to identify districts with low immunization coverage and guide mop-up actions during the last 4 days of a combined oral polio vaccine (OPV) and yellow fever (YF) vaccination campaign conducted in Cameroon in May 2009. We monitored 17 pre-selected districts at risk for low coverage. We designed LQAS plans to reject districts with YF vaccination coverage <90% and with OPV coverage <95%. In each lot the sample size was 50 (five clusters of 10) with decision values of 3 for assessing OPV and 7 for YF coverage. We ‘rejected’ 10 districts for low YF coverage and 14 for low OPV coverage. Hence we recommended a 2-day extension of the campaign. Clustered-LQAS proved to be useful in guiding the campaign vaccination strategy before the completion of the operations.

Corresponding author
*Author for correspondence: Dr L. Pezzoli, Epidemiology Consultant, World Health Organization, Geneva, Switzerland. (Email:
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Epidemiology & Infection
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