Use of Lot Quality Assurance Sampling (LQAS) to estimate vaccination coverage helps guide future vaccination efforts

Abstract

SummaryInadequate evaluation of vaccine coverage after mass vaccination campaigns, such as used in national measles control programmes, can lead to inappropriate public health responses. Overestimation of vaccination coverage may leave populations at risk, whilst underestimation can lead to unnecessary catch-up campaigns. The problem is more complex in large urban areas where vaccination coverage may be heterogeneous and the programme may have to be fine-tuned at the level of geographic subunits. Lack of accurate population figures in many contexts further complicates accurate vaccination coverage estimates. During the evaluation of a mass vaccination campaign carried out in N'Djamena, the capital of Chad, Lot Quality Assurance Sampling was used to estimate vaccination coverage. Using this method, vaccination coverage could be evaluated within smaller geographic areas of the city as well as for the entire city. Despite the lack of accurate population data by neighbourhood, the results of the survey showed heterogeneity of vaccination coverage within the city. These differences would not have been identified using a more traditional method. The results can be used to target areas of low vaccination coverage during follow-up vaccination activities.

Reported community-level indoor residual spray coverage from two-stage cluster surveys in sub-Saharan Africa

“…LQAS is commonly used to estimate vaccination coverage [15], a similar intervention to IRS in that population-level coverage is perhaps more important for preventing transmission of disease than individual or household-level coverage [16]. For IRS, the malaria vector is killed while resting on the wall of a household after the mosquito has taken a blood meal thereby making household-level coverage somewhat beneficial to neighbours and community-level coverage more important for controlling malaria transmission.…”

Vaccine Coverage Rates Among 12-23 Month Old Children Living in Four Selected Provinces of Turkey: Results of a Lot Quality Survey

“…11,[13][14][15][16][17][18][19] The main reasons for common use of LQT in vaccine-related research is its ease in application, no need for a sampling frame record and/or large population size; ability to determine performance of individual sub-units in the population to identify those with "unacceptably low" coverage rates; and the possibility of chosing a range of different confidence intervals, and accuracy levels. LQAS may require a larger initial investment than administrative or cluster survey methods owing to larger sample sizes.…”

Outbreak response immunisation: the experience of Chad during recurrent measles epidemics in 2005 and 2010

“…VC surveys were conducted immediately after both campaigns using Lot Quality Assurance Sampling (LQAS). 6 Between January and April, 7822 cases were reported in 2005 and 8481 cases in 2010, corresponding to global attack rates of 64.6 per 10 000 population and 54.5 per 10 000 population, respectively (Figures 1 and 2 7,8 The city was divided into 25 non-overlapping lots based on administrative neighbourhoods with well known boundaries in 2005. In 2010, three additional lots were included in the survey to match the new administrative distribution of the city.…”