Immunization, Vaccines and Biologicals

Immunization coverage


Survey methods

Surveys aim to estimate the levels of immunization coverage at either national or sub-national levels. They aim to either establish baseline information and to provide a comparison with administrative estimates (to verify administrative coverage data), while efforts to improve routine reporting systems are ongoing. They can also be used to respond to specific questions regarding factors associated to coverage or to satisfy information demands of the partner agencies.

Although the primary objective of an immunization coverage survey is to provide a coverage estimate for selected vaccines or a set of vaccines (fully vaccinated for age) among infants, children and/or women of childbearing age, etc, other information, which is usually not available through routine monitoring systems, can be obtained.

WHO/A.Jenny

Furthermore, surveys facilitate assessing equity in immunization, by allowing disaggregating coverage by factors such as place of residence, sex, maternal education, economic status or subnational region.

Vaccination Coverage Surveys can be complemented with serosurveys. Serosurveys can help establish baseline prevalence of a vaccine-preventable disease prior to the introduction of a particular vaccination policy, or to assess the impact of such vaccine programme. Serosurveys have been mainly used for Hepatitis B and measles.

The WHO vaccination coverage survey

Since the early 1990s, the World Health Organization (WHO) has provided guidance to Member States, partner agencies and institutions on methods for measuring immunization coverage through surveys and has provided manual and tools to conduct the EPI cluster survey.

With the goal of improving survey precision, accuracy, and overall quality, an extensive review and revision of coverage survey methods and materials resulted in the release, in 2015, of the working draft of WHO Vaccination Coverage Cluster Survey Reference Manual.

While the statistical methods outlined in the new Survey Reference Manual are commonly used on large household health surveys, such as DHS and MICS, Immunization Programmes may be less familiar with them. Therefore, WHO is preparing tools to facilitate the management, analysis, presentation and interpretation of survey. One of these tools, “Vaccination Coverage Quality Indicators (VCQI)” is set of scripts in STATA and R a program intended to be used by data managers to manage entering and cleaning survey data; statisticians and epidemiologist to analyse survey data; and for programmers to add further modifications and additional analysis. A beta version of VCQI can be obtained by emailing vpdata@who.int.

Other survey types used to monitor vaccination coverage include:

  • international household survey initiatives, such as UNICEF Multiple Indicator Cluster Survey (MICS) and the Demographic and Health Surveys (DHS)Program
  • the Lot Quality Assurance (LQA) technique, mostly used to assess polio supplementary immunization activities (vaccination campaigns).

Resources

New WHO Vaccination Coverage Cluster Survey Manual
2005 Immunization coverage cluster survey : reference manual
Other useful resources

Last Update: 20 April 2016

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