What is vaccine delivery?

What is vaccine coverage?

We measure success in vaccine delivery by monitoring vaccine coverage. Vaccine coverage is the percentage of a vaccine’s target population that has been vaccinated. The target populations differ by vaccine, but they typically comprise those who are at greatest risk of contracting and transmitting a particular disease. Infants are vulnerable to more diseases than adults; consequently, they are typically the most important target population. To measure the effectiveness of an immunization system, coverage of the third dose of the DTP vaccine (DTP3) is often used. This DTP3 coverage is the percentage of infants in a community that receive all three recommended doses of the diphtheria, tetanus, and pertussis vaccine that they need before their first birthday.)

As a community’s vaccine coverage rises, the risk for all members of the community, even those unable to be vaccinated, falls. And as infection rates decrease, the human and economic burden of disease is likewise reduced. This improves health and productivity for individuals and communities alike.

Vaccine coverage serves as an indicator of a health system’s ability to provide basic care to all. Looking more closely at coverage within communities can also reveal inequities in access to health services—due to wealth, education, or location, for instance. Since diseases continue to circulate among un- and under-vaccinated people and communities, these inequities have consequences for everyone.

Who needs vaccines, and what vaccines do they need?

The World Health Organization (WHO) recommends a set of essential vaccines for every child, everywhere. These vaccines protect against serious childhood diseases such as diarrhea, diphtheria, hepatitis, measles, meningitis, pertussis, pneumonia, polio, rubella, tetanus, and tuberculosis. Ideally, children should get most of these essential vaccines before their first birthday, with booster doses to extend protection in childhood and adolescence.²

The WHO also recommends additional vaccines that prevent disease in other at-risk people and communities. For example, all adolescent girls should receive the human papillomavirus (HPV) vaccine to prevent many types of cancers. Pregnant women should be vaccinated against tetanus to protect both mother and infant in the first months of life. And in communities where diseases such as cholera, dengue, Japanese encephalitis, typhoid, and yellow fever are endemic, vaccines can help prevent and control outbreaks.

How do we track vaccine coverage?

Vaccine coverage is the percentage of a vaccine’s target population that has been vaccinated.

Health facilities track vaccine coverage based on the number of doses they administer and the population they serve. This information is compiled at the district, state, and national levels, and countries report their results annually to WHO and UNICEF.

At the same time, in many countries, periodic community-based surveys help researchers understand how geographic, demographic, and social characteristics influence health. These surveys, which include Demographic Health Surveys (DHS) and Multiple Indicator Cluster Surveys (MICS), also provide valuable data on vaccine coverage, especially in places where health workers may not be sure how large a target population is.

For simplicity, coverage with all three doses of the diphtheria-tetanus-pertussis vaccine (referred to as DTP3) is often used as a key indicator of performance. The percentages of Fully Immunized Children (FIC), or children who receive all recommended doses of all recommended vaccines by their first birthday, and zero-dose children, who receive no DTP before their second birthday, are also important performance indicators.

Why is coverage important?

Vaccine coverage helps predict the risk of disease within a community. It is also a measure of a health system’s ability to provide basic care to all.

Coverage and disease risk

Immunization has contributed to striking reductions in child mortality over recent decades. For example, measles vaccination alone has prevented an estimated 21 million deaths between 2010 and 2017.³

Vaccines protect in two ways: the direct protection of vaccinated children, and the indirect protection of unvaccinated people through population immunity. Direct protection is achieved when a child has received the recommended number of doses of a vaccine at the appropriate ages. Population immunity, also known as “herd immunity,” occurs when enough members of a population have been vaccinated against a disease to stop its spread. This indirectly protects unvaccinated people by reducing their exposure to disease-causing organisms.

To protect immune-compromised people and children too young to be fully vaccinated, and to limit the frequency and spread of outbreak-prone diseases such as cholera, measles, meningitis, and yellow fever, achieving and maintaining population immunity is critical.

Coverage and system performance

Because every child should be immunized as part of routine preventive health care, vaccine coverage data show how well a health system is serving its community. Coverage data are also used to target health system improvements. By focusing on un- and under-vaccinated people (those who have not received the full set of recommended vaccines), health systems can find and serve families with poor access to care. This, in turn, can reduce inequities in access to health services.

What are the broader benefits of high vaccine coverage?

Saving healthcare costs and improving productivity

As fewer people suffer illness, disability and death from infectious diseases, families and societies spend less time and money on treating the sick. That means more people can live healthy, productive lives—benefits that far exceed the cost of vaccination. An analysis of 10 vaccines in 94 low- and middle-income countries estimated a 44-fold return on investment between 2011-2020. In other words, every dollar invested in immunization saves $44 in cost and productivity.⁴

Supporting delivery of other health services

In most low-resource settings, immunization programs reach more people than any other health care interventions—which means immunization programs can also help deliver other primary health care services. For example, immunization clinics often deliver nutritional interventions such as vitamin A supplementation and growth monitoring. In this way, vaccine delivery can improve the efficiency and effectiveness of the health system as a whole.