On May 1, according to CDC, the seven-day moving average of new COVID-19 cases in the United States was just under 50,000—the lowest such figure since October. Roughly 45 percent of the U.S. population has received at least one dose of a COVID-19 vaccine, and 32 percent are fully vaccinated. Looking specifically at one of our most susceptible demographics, 83 percent of those 65 and older have received at least one dose, with 70 percent fully vaccinated.

Balancing these encouraging numbers are data indicating that the rate of vaccinations administered has slowed over the last few weeks: as of April 30, the most recent day for which such data are available, the seven-day moving average of total doses administered was just over 2.1 million, falling steadily from a high of 3.27 million on April 11.

The drop-off in vaccinations potentially indicates that the portion of the population who are most readily accepting of vaccines has already received their shots. Those who remain are likely to exhibit some degree of “vaccine hesitancy,” which the World Health Organization defines as delayed acceptance of or refusal of vaccines despite the availability of vaccine services (PDF).

Individuals may be hesitant about vaccines for many possible reasons. These include concerns about the safety of vaccines and distrust of the government, the medical community, or pharmaceutical companies, according to Framework for Equitable Allocation of COVID-19 Vaccine, a 2020 publication of the U.S. National Academies of Sciences, Engineering, and Medicine. Some hesitant individuals might be waiting for more information about the vaccines; others, particularly in minority communities, may be alarmed by appalling instances of discrimination such as the Tuskegee syphilis study. Still others may be concerned by the unprecedented speed with which the COVID-19 vaccines were developed or by the novel mRNA technology used by some vaccine manufacturers.

Acknowledging that the continuing effectiveness of vaccination efforts depends upon reaching vaccine-hesitant individuals, the National Academies recently released a new document that summarizes strategies for communicating about vaccines. “Understanding and Communicating about COVID-19 Vaccine Efficacy, Effectiveness, and Equity” presents the following practical tips:

Define terms clearly. The publication notes that the three vaccines currently authorized for use in the U.S. have different defined endpoints for determining “efficacy,” which the public may find confusing. One way to reduce confusion may be to consistently focus messaging on the same endpoints—for example, severe illness, hospitalization, and death.

Use numbers to describe quantities. For example, when talking about the side effects of vaccines, don’t just describe them as “rare”—state how rare they are.

Compare options clearly. Well-designed communications will avoid focusing on single issues such as vaccine side effects. Tables can be used to highlight, for example, the effects of both choosing and declining vaccination.

Present all relevant outcomes. For some individuals, evidence regarding vaccines’ ability to limit hospitalizations may be most important; others may focus more on evidence regarding instances of disease with severe symptoms. Messaging that addresses the full range of outcomes is more likely to be effective with more people.

Communicate uncertainty and anticipate changes. Acknowledge, for example, that cases of mild disease among vaccinated people are to be expected and that their absolute numbers will increase as vaccination efforts reach more people.

Communicating science effectively is notoriously difficult; as the authors of the new National Academies report acknowledge, “presenting the science on COVID-19 vaccines does not guarantee that people will accept recommendations or modify their behavior accordingly.” The suggestions in the report are based on research in what the National Academies has called “the science of science communication.” For more insight regarding this topic, see the resources below, all of which are freely available.

Resources

The National Academies Press: Communicating Science Effectively: A Research Agenda (2017).

The National Academies Press: Framework for Equitable Allocation of COVID-19 Vaccine (2020).

The National Academies Press: “Understanding and Communicating about COVID-19 Vaccine Efficacy, Effectiveness, and Equity” (2021).

Proceedings of the National Academy of Sciences: The Science of Science Communication (August 2013).

Proceedings of the National Academy of Sciences: The Science of Science Communication II (September 2014).