evidence: In a sign of limited public enthusiasm for COVID-19 vaccines, only about a third of U.S. adults have the highest level of available protection against the coronavirus, saying they have been fully vaccinated and have received a booster shot within the last six months. (Booster shots designed for newer variants of the coronavirus have been available since September 2022, about six months before the survey was conducted.) A similar share say they were fully vaccinated but have not received a booster shot in the past six months and about a fifth of U.S. adults say they have not been vaccinated against COVID-19. [...] People who have been fully vaccinated but have not received a recent booster in the past six months fall somewhere in the middle, with a mix of positive and negative views about the coronavirus vaccines. For example, a majority of this group (72%) sees the statement that "COVID-19 vaccines have saved millions of lives" as being at least somewhat in line with their views. At the same time, a majority of this group (63%) also says the statement "we don’t really know if there are serious health risks from these vaccines" describes their views at least somewhat well. [...] Those who are recently boosted and fully vaccinated against COVID-19 are the most likely to be concerned about getting a serious case of the disease.