As the world continues to move toward a post-pandemic life — and as the World Health Organization (WHO) recently predicted that COVID-19 will end in 2023 as a public health emergency — Americans may have reached a state of "vaccine fatigue," data suggests.

A recent study published in the journal Nature Medicine, led by researchers from the Medical University of Vienna, surveyed 6,357 people in Austria and Italy. They found that respondents’ "readiness to get vaccinated," on a scale of 0 to 10, was relatively low — roughly 5.8 in Italy and 5.3 in Austria.

The participants answered questions about vaccine-related costs, communication, incentives, emerging variants of the virus and vaccination requirements.

The American Medical Association defines vaccine fatigue as "unwillingness or inaction toward vaccine information or instruction due to perceived burden or burnout."

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In the U.S., evidence of vaccine fatigue can be seen in the dwindling numbers of people getting boosters for COVID vaccines.

When the vaccines first became available in the summer of 2021, there was a wave of relief — even enthusiasm in some corners — as people lined up to get the shot. By Sept. 1, 2022, 79.2% of Americans had gotten at least one dose and 67.8% had completed their full primary series of vaccines, per the Centers for Disease Control and Prevention (CDC).

There is a sharp drop-off, however, when it comes to booster numbers.

As of March 21, 2023, only 16.4% of Americans were current with their updated (bivalent) booster dose, CDC data shows.

Low trust in medical institutions, governments and vaccinations was a common thread in the study findings, particularly around vaccine mandates.

"Respondents in both countries reported high levels of pandemic fatigue and showed low to medium levels of trust in parliament and government," the study authors wrote in a discussion of the findings.

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Dr. Shana Johnson, a physical medicine and rehabilitation physician in Scottsdale, Arizona, was not involved in the study but reviewed the findings. 

"A pertinent finding was that vaccine mandates showed no visible effects on the likelihood to get vaccinated, but strongly affected the trust in vaccines negatively," she told Fox News Digital.

"Per the study, a more effective strategy to encourage vaccination is to promote community spirit while retaining medical choice," she added.

Some refuse the vaccine simply because they believe they don’t need it — and in some cases, they may be right, Dr. Johnson noted.

"The COVID virus' virulence or danger varies tremendously based on age and risk factors," she said. "It is not the same disease in a 10-year-old, a 40-year-old and a 70-year-old. If you are young with no underlying medical conditions and your past COVID infection caused a stuffy nose for two days, you are not going to see a great need for repeat vaccination."

On the other hand, for those over 65 with risk factors for severe disease, the need is much clearer, Dr. Johnson said. 

Dr. Norman B. Gaylis, medical director at the Immunotherapy Center of South Florida and an expert on long COVID, said there are numerous reports and studies indicating that people have not only lost interest in being vaccinated, but are also tired of hearing about new variants, boosters and vaccine updates.

"In my opinion, some people have lost faith in being protected by vaccination for a number of reasons," he told Fox News Digital. 

"For example, they may have gotten COVID after getting vaccinated, or they may have heard conflicting viewpoints and controversies about adequate protection or adverse side effects of vaccination."

Dr. Gaylis added, "Unfortunately, many people believe that COVID is no longer a serious health threat they should be concerned about."

The Medical University of Vienna study found that certain groups tended to display higher levels of fatigue than others.

Those who had never received any COVID vaccine responded that they would refuse the vaccine in nearly all presented scenarios, the researchers stated.

People who had received at least one or two vaccine doses seemed much more likely to agree to get a booster if offered positive incentives.

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Those who had gotten three or more doses were the most open to returning for boosters — if they were available, easily accessible and recommended by experts.

For patients who have COVID fatigue and no longer believe they need vaccines, Dr. Gaylis recommends that health care professionals help them weigh the pros and cons before recommending a customized treatment or prevention plan. 

"They should discuss the medical evidence in favor of vaccination for protection and immunity," he said.

The findings from the Vienna study identified several approaches to countering vaccine fatigue.

"We recommend offering adapted vaccines at different times of year, retaining low-threshold access to vaccinations and ensuring that people take experts’ views into account in order to maintain high levels of immunization among the population in future," said lead researcher Tanja Stamm, professor and head of the Institute for Outcomes Research at the Medical University of Vienna, in a discussion of the findings. 

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Communication campaigns are not as effective as they once were, the study also suggests — and positive incentives could be used to persuade certain groups who may be resistant to more vaccine, it also indicates.

Dr. Marc Siegel, clinical professor of medicine at NYU Langone Medical Center and a Fox News medical contributor, agreed that vaccine fatigue will be a significant factor going forward.

"I think the main strategies should be to concentrate on the group that is already boosted, to circulate information on the vaccine effects waning, and to share recent studies showing that boosters decrease the impact of long COVID," he told Fox News Digital.

In addition to offering incentives, Siegel also said he supports minimizing the cost to obtain vaccines and upgrading the vaccines so they better match the latest variant. 

Listening to people’s fears is also key, said Dr. Johnson. 

"Those who have not studied medicine for the past 20 years do not process the COVID science the same," she told Fox News Digital. "We need to listen, understand their perspective and meet them there in our discussions."

One thing the Vienna vaccine fatigue study was not able to address was the presence of COVID antibodies in those who have been vaccinated or have had the virus, Dr. Gaylis noted. 

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"Many of those individuals may have adequate levels of antibodies, and if they do, they may not need additional vaccination," he said. 

"This is a question that, as a medical professional having treated over 2,000 patients with COVID and long COVID, I cannot answer." 

"I can say there are groups [of people] that must seriously consider getting vaccinations and boosters, such as high-risk individuals with diabetes, obesity and the immunocompromised," he added.