Assessing and monitoring vaccination coverage levels: lessons from the Americas.

1 Pan American Health Organization, Immunization Unit, Washington, D.C., United States of America (currently assigned to the Centers for Disease Control and Prevention, National Immunization Program, Global Immunization Division, Atlanta, Georgia, United States of America). Send correspondence to: Vance Dietz, Global Immunization Division, National Immunization Program, Centers for Disease Control and Prevention, 1600 Clifton Rd., MS E05, Atlanta, Georgia 30333, United States of America; telephone: 404-639-6225; fax: 404-639-8572; e-mail: [email protected] 2 Pan American Health Organization, Immunization Unit, La Paz, Bolivia (currently assigned to the Centers for Disease Control and Prevention, National Immunization Program, Global Immunization Division, Atlanta, Georgia, United States of America). 3 Pan American Health Organization, Immunization Unit, Washington, D.C., United States of America (currently with the United States Food and Drug Administration, Rockville, Maryland, United States of America). 4 Private consultant, Donnelly, Idaho, United States of America. 5 United States of America, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America. 6 Pan American Health Organization, Immunization Unit, Mexico City, Mexico (currently assigned to the Centers for Disease Control and Prevention, Global AIDS Program, Guatemala City, Guatemala). 7 Pan American Health Organization, Family and Community Health Area, Washington, D.C., United States of America. The Pan American Health Organization (PAHO) has made the achievement of high vaccination coverage levels a key goal for the Region of the Americas. Achieving coverage levels of 95% or higher at the national and local levels is central to PAHO’s objectives of eliminating measles and rubella, controlling vaccine-preventable diseases, and maintaining polio eradication in the Americas (1–3). Besides the national coverage levels, PAHO currently recommends that countries utilize two other measures or indicators of coverage for each vaccine: (1) the number and proportion of municipalities (i.e., districts) with a vaccine-specific coverage level of ≥ 95%, and (2) the number and proportion of children in a given age group who live in a municipality with ≥ 95% coverage.8 These three measures of coverage enable national programs to identify high-risk municipalities and to ensure equity in the provision of immunization services (4). Implicit in adopting coverage goals is the ability to measure and monitor vaccination coverage levels. Countries in the Americans annually report coverage levels to PAHO that are based on the administrative method (doses administered), which is a method that PAHO recommends (5). The method involves dividing the number of doses of a particular vaccine that were given (the numerator) by the number of persons who should have received that vaccine (the denominator). Using population figures for the Western Hemisphere, PAHO then calculates Regional coverage levels for all the vaccines in its Expanded Program on Immunization (EPI). Some countries employ coverage surveys utilizing various methodologies to estimate coverage. PAHO encourages the use of a “rapid house-tohouse monitoring tool” to assess the quality of vaccination activities in a given area (6). In addition, serologic surveys can be conducted to measure the immunologic protection that a community has against vaccine-preventable diseases. Each coverage assessment methodology has advantages and disadvantages. Therefore, national program managers must be aware of the strengths and limitations of each methodology as well as when a particular methodology is indicated for use. In this piece we will review currently available op