In Brief

COVID-19: Why Vaccination Coverage Is Important

Vaccines are a major public health success story, but the COVID-19 pandemic underscores the many challenges involved in getting a vaccine to everyone who needs it.

The coronavirus pandemic has highlighted the challenges of not only developing vaccines, but also making sure everyone who should get them does. High hopes have been placed on the global distribution of promising vaccines from Pfizer and BioNTech and from Moderna, among others, but vaccination campaigns can face many hurdles: limited availability, public mistrust, and dosage and storage requirements can all jeopardize vaccination coverage. A look at previous vaccine distribution efforts showcases some of the main challenges.

How do existing vaccines stack up?

Public health experts consider vaccines to be among medicine’s most important achievements, helping to reduce the prevalence of some diseases—such as polio—to near zero worldwide. Yet, even for diseases with vaccines, achieving and maintaining high coverage can be difficult. The World Health Organization (WHO) has warned of a “dangerous stagnation” of vaccination rates in recent years.

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There are many factors that affect a vaccine’s coverage rate. These include:

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Availability. Countries can face vaccine shortages for a range of reasons, including conflict and insufficient production capacity. The WHO has noted a global shortage [PDF] of the human papillomavirus (HPV) vaccine in recent years due to limited manufacturing capacity amid rising demand. In the case of the COVID-19 crisis, production capacity is being tested on an unprecedented scale, with vaccine makers turning to dozens of third-party manufacturers in order to fulfill orders for hundreds of millions of doses. U.S. distribution has already seen hiccups: Pfizer executives and state and federal officials offered conflicting information on state allotments in the first week of the vaccine rollout.

Distribution also presents a hurdle. Some vaccines, such as that for chickenpox (varicella), must be kept at very low temperatures when transported and stored, a process known as the cold chain. While this is typically an issue only for rural or remote areas, several COVID-19 vaccines pose broader cold-chain challenges: the Pfizer-BioNTech vaccine must be stored at -70°C (-94°F), meaning warehouses, trucks and planes, and points of care all require ultra-cold freezers.

A boy receives polio vaccine drops during an immunization campaign in Karachi, Pakistan.
A boy receives polio vaccine drops during an immunization campaign in Karachi, Pakistan. Akhtar Soomro/Reuters

Public understanding and trust. Health officials can build trust in their communities through clear and transparent communication about vaccines. This includes information about their effectiveness, any expected side effects, and when to return for booster shots. Experts have raised alarm about increasing vaccine skepticism, which has led to measles outbreaks in a number of countries. Mistrust similarly undermined efforts to fight Ebola outbreaks in the Democratic Republic of Congo. Hesitancy about COVID-19 vaccines is high in the United States, with roughly 40 percent of Americans surveyed saying they would not get one if it were available now. Only 37 percent said they would be comfortable being among the first to get vaccinated. “There will have to be a terrific amount of education, coupled with reassurance,” says William Schaffner, a professor at the Vanderbilt University School of Medicine.

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Complexity of the vaccine series. Sometimes two or more doses are recommended for maximum protection, with weeks or even months between doses. The Moderna and Pfizer-BioNTech vaccines both require two doses, and individuals will have to receive the same vaccine for both doses. Schaffner says this will require a meticulous tracking system.

Recommendations. Health authorities often designate a vaccine for particular age groups or for people that share certain health risks. In the United States and some other countries, visits to the pediatrician are largely determined by vaccination schedules, making it much easier to achieve high coverage among infants and toddlers. Teens and adults typically don’t make routine doctor visits, lowering their coverage. The U.S. Centers for Disease Control and Prevention has issued guidance for a phased COVID-19 vaccination campaign, with health-care workers and residents of nursing homes and long-term care facilities first in line.

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How do these variables affect coverage globally?

Recommendations for a particular vaccination can vary significantly across countries. For example, in the United States, an annual flu vaccine is recommended for anyone six months or older, while in some European countries, such as Belgium and Lithuania, it is only recommended for high-risk groups, which include health-care workers, pregnant women, and people with weakened immune systems. As a result, coverage rates can look very different around the globe.

The WHO’s Europe office has expressed concern about declining use of influenza vaccines across the region, citing limited procurement of vaccines, health-care providers not advising the vaccination, out-of-pocket costs, and low public confidence.

How is the pandemic affecting vaccination coverage?

Amid the coronavirus pandemic, a major concern among health experts has been a drop in coverage for routine vaccinations, as many families avoid visits to doctors’ offices and pharmacies out of fear they could be exposed to COVID-19.

Health officials around the globe have urged citizens to get their flu shot to avoid a “twindemic” of seasonal influenza and COVID-19. In the United States, more than seventy million doses of the flu vaccine were administered to adults by late November—up from about fifty-nine million a year earlier—and the number of flu cases appeared unusually low.

What’s in store for COVID-19 vaccinations?

Even in the best of times, successful vaccination policy involves many moving parts. In the COVID-19 crisis, it’s the entire global population that needs protection, and scientists and health officials are working to achieve that within an unprecedented timeframe. Ultimately, developing safe and effective vaccines is only the beginning. “It’s not a magic wand,” says Vanderbilt’s Schaffner. “It won’t make the virus disappear.” It will take months before vaccinations are widely available to the public in wealthier countries, and even longer in poorer countries that are struggling to secure enough doses. That means following safety guidelines, such as physical distancing and mask wearing, for some time to come.

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