The use of LQAS to assess polio immunization coverage in Nigeria

Ensuring consistently reliable monitoring data of supplementary immunization activities (SIAs) is a key factor to ensuring that polio eradication strategies are effectively implemented. A new tactic of the new Global Polio Eradication Initiative Programme of Work 2010–2012 will be to ensure enhanced monitoring of SIAs, both in endemic and outbreak areas.

To this effect, the World Health Organization has been adapting and testing the Lot Quality Assurance Sampling (LQAS) method, which classifies areas of interest corresponding to “lots” as having acceptable or unacceptable levels of vaccine coverage, to evaluate vaccination programmes in developing countries.

Conducting LQAS surveys in the field is straightforward: if in a sample of individuals the number of unvaccinated exceeds a pre-set decision value, then the area (lot) is classified as having an unsatisfactory level of vaccine coverage and mop-up activities are recommended. This ease of application makes the LQAS a very operational tool to detect pockets of low vaccine coverage and therefore direct focused vaccination efforts.

In Nigeria, the Global Polio Eradication Initiative piloted a study to assess OPV coverage in 20 local
government areas (LGAs) in five high-risk states using LQAS during the November 2009 Immunization Plus Days.

Two LGAs were accepted at target coverage of 90%, seven rejected with coverage below 90%, a further seven rejected with coverage below 70% and four rejected with coverage below 50%.

The pilot proved that LQAS is feasible and useful for the polio eradication programme to efficiently monitor and guide future OPV campaigns in Nigeria and other polio-infected countries.