In Brief

COVID-19: Why Vaccine 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 a vaccine, but also making sure everyone who should get it does. High hopes have been placed on the rapid development of a COVID-19 vaccine, but to be successful it must overcome many hurdles: limited availability, public mistrust, and dosage and storage requirements can all jeopardize vaccine 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 governments including the United States’ funding production of millions of doses of several vaccines before they are approved. 

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 experimental COVID-19 vaccines pose broader cold-chain challenges: Pfizer’s vaccine must be stored at -70°C (-94°F), meaning warehouses, trucks and planes, and points of care would all need 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 a COVID-19 vaccine is already high in the United States, with nearly half of Americans saying they would not get one if it were available now. Adding to that is the possibility that the Food and Drug Administration (FDA) will make an emergency-use authorization for some COVID-19 vaccines before full data from clinical trials is available.

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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. Two of the leading candidates for COVID-19 vaccines—Moderna’s and Pfizer’s—require two doses, and appear to come with side effects. “When you get it, it hurts: swelling, redness, soreness, limitation of arm motion, maybe headaches,” says William Schaffner, a professor at the Vanderbilt University School of Medicine. “And so getting a person to come back, that will take some persuasion.” Moreover, individuals must receive the same vaccine for both doses, which will require a meticulous tracking system to avoid mishaps.

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 vaccine schedules, making it much easier to achieve high coverage among infants and toddlers. But teens and adults typically don’t make routine doctor visits, lowering their coverage.  

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Health Policy and Initiatives

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How do these variables affect coverage globally?

Recommendations for a particular vaccine 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 for a particular vaccine 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 vaccine coverage?

Amid the coronavirus pandemic, a major concern among health experts has been a drop in coverage for routine vaccines, 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 are urging citizens to get their flu shot to avoid a “twindemic” of seasonal influenza and COVID-19. In the United States, major pharmacy chains Rite Aid and Walgreens projected surges in flu-shot demand of up to 50 percent, and manufacturers expect to distribute a record number of doses—close to two hundred million. 

What’s in store for a coronavirus vaccine?

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 are working to achieve that within an unprecedented timeframe. Ultimately, developing a safe and effective vaccine will only be the beginning. “It’s not a magic wand,” says Vanderbilt’s Schaffner. “It won’t make the virus disappear.” That means following safety guidelines, such as physical distancing and mask wearing, for some time to come.

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