Close Reasons for Covid-19 vaccine hesitancy are many; here's what medical and public-health experts say about some concerns By Melissa Patrick Kentucky Health News May 3, 2021 May 3, 2021 In a society that gives out trophies for participation, it's only natural that the U.S. is celebrating that about a third of its population is fully vaccinated against the coronavirus and 43% have received at least one dose of a vaccine.  But hold those trophies, public health officials might say, because we have a ways to go before we reach herd immunity that will offer a level of protection for those who can't or won't get a vaccine -- and to keep the virus from spreading and mutating, perhaps into more contagious variants.