Researchers Find Vaccine Hesitancy Would Hamper COVID-19 Efforts

Even if a vaccine for the novel coronavirus COVID-19 is developed and made widely available, about 20 percent of Americans will likely decline to receive it, according to a study by University of Wyoming economists.

As a result, the researchers project that it is likely the vaccine will fail to ensure herd immunity — a condition in which people are sufficiently immune to the virus such that the pandemic dies out.

“A vaccine for COVID-19 might be the best hope for ending the pandemic. Scientists are, therefore, racing to develop a vaccine, in unprecedented joint efforts within the scientific community,” the UW economists say. “However, the challenge to extinguish the novel coronavirus does not end with finding an effective vaccine. The implementation of the vaccine program will be important.”

The paper, which may be viewed here, is the latest in a series of coronavirus-related studies conducted by UW College of Business economist Linda Thunstrom, graduate student Madison Ashworth, of Star Valley, and Professor David Finnoff and Assistant Professor Stephen Newbold.

The research, based on data collected primarily March 24-31, involves a randomized controlled trial with a nationally representative sample of 3,133 participants who were asked to state their intention to vaccinate themselves and their children when a COVID-19 vaccine becomes widely available.

Those participating in the study were presented with four different scenarios, with variation in the probability of coronavirus infection and conditional mortality rates — and an assumption that a COVID-19 vaccine would be 60 percent effective. The study also examined how vaccine avoidance would be affected if the White House communicates lower risks from COVID-19 than the Centers for Disease Control and Prevention (CDC).

The results showed that 13 to 30 percent — or an average of 20 percent — of people would decline a vaccine for COVID-19. People avoid the vaccine mainly because of general vaccine hesitancy, distrust of vaccine safety and vaccine novelty.

Also influencing people’s willingness to be vaccinated is discrepancy in risk articulated by public officials. Those who were given the White House projection with a more optimistic view of COVID-19 risks — lower probability of becoming infected, compared to the risk communicated by public health officials — were less likely to be vaccinated than those given the projections by public health officials only.

“We find that inconsistent information from government authorities about COVID-19 risks may affect not only risk perceptions, but also health-related behaviors — vaccine avoidance increases if the White House communicates lower risks to COVID-19 than does the CDC,” the economists wrote.

Estimates of basic reproduction numbers for the novel coronavirus imply that herd immunity could be achieved when somewhere between roughly 60 and 80 percent of the population is immune, either from a vaccine or previous infection. Taking all factors into account — vaccine avoidance, vaccine effectiveness, current estimates of COVID-19 infectiousness and an assumed low level of immune individuals — the UW economists say their epidemiological model shows that a vaccine program in an upcoming COVID-19 season is likely to fail to ensure herd immunity, even if the vaccine is made available to the entire population.

If, however, it turns out that people who have recovered from COVID-19 become immune — which currently is unknown — the vaccine has better chances of succeeding in achieving herd immunity. Even though the vaccine may fail to ensure herd immunity, it would still help mitigate the COVID-19 pandemic in the United States.

“Measuring the share of the population who may be reluctant to be vaccinated for COVID-19 can help policymakers, health care workers and other authorities to plan ahead toward minimizing the impact on public health from vaccine hesitancy,” the researchers wrote. “This might involve tailored public communication programs designed to persuade vaccine-hesitant individuals to take the vaccine, or increased efforts to ensure that the vaccine uptake level among the remainder of the population is as high as possible, or both.”

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