Immunization, Vaccines and Biologicals

Systematic review of missed opportunities for vaccination

Request For Proposals

Introduction and Background


This request for proposals (RFP) is made by the WHO Department of Immunization Vaccines and Biologicals (IVB). IVB seeks proposals for the rigorous systematic review and meta-analysis of all available data from published and unpublished studies relevant to missed opportunities for vaccination. IVB encourages proposals that include collaboration between institutions/groups in industrialized countries and institutions/groups in low and middle income countries.


As early as 1983, the Expanded Programme on Immunization (EPI) has recommended using every opportunity to immunize all eligible people as a direct strategy to increase vaccination coverage. Protocols for the assessment of “missed opportunities” (defined as any contact with a health service that did not result in an eligible child or woman receiving the needed vaccines) were developed in 1984 and 1988 and widely distributed.

Missed opportunities for vaccination occur in two major settings:

  • during visits for immunization and other preventive services (e.g. growth monitoring, nutrition assessments and oral rehydration training sessions, etc.).
  • during visits for curative services.

In both settings, eliminating missed opportunities has the potential to raise immunization coverage in a population, particularly when the availability and use of health services is high. When the availability and use of health services is low, immunizing at health care contact is extremely important because the risk for vaccine-preventable diseases is likely to be high in these areas.

Many missed opportunity assessments were conducted throughout the 1980s and 1990s, and were summarized in a WHO commissioned global review published in 1993. At the time, it was found that there were missed opportunities to vaccinate an estimated 30% of children and women. The most important reasons for missed opportunities were:

  • The failure to administer simultaneously all vaccines for which a child was eligible;
  • False contraindications to immunization;
  • Health worker practices including not opening a multi-dose vial for a small number of persons to avoid vaccine wastage;
  • Logistical problems, such as vaccine shortages, poor clinic organization, and inefficient clinic scheduling.

At the request of the Strategic Advisory Group of Experts (SAGE) in November 2007, WHO made a detailed analysis of the epidemiology of the unvaccinated and under-vaccinated (partially vaccinated) children. The analysis took a three-pronged approach: (1) analysis of demographic and health surveys (DHS) and multiple indicator cluster surveys (MICS) of 95 countries; (2) a review of data in the gray literature; and (3) a review of the data published in scientific journals. Included in this were many missed opportunity assessments.

The analysis found that a large proportion (44%) of the reasons for under-vaccination were factors related to the Immunization System including: Access and vaccine service availability; Use of all opportunities; Cost and service quality; and Health worker knowledge. In order to address these issues, there was renewed interest in missed opportunities assessments as a simple tool for the management of immunization programmes, providing practical data for decision-making to improve immunization coverage.