Time for a fourth Covid vaccine dose? Here's why medical professionals are skeptical

Countries are beginning to offer a fourth dose of the Covid-19 vaccine to vulnerable groups, but medical professionals are undecided on whether it would benefit the wider population. The U.S. FDA has so far authorized a fourth shot only for those aged 50 and above, as well as those who are immunocompromised. And the U.S. CDC was skeptical of the need for a fourth dose for healthy adults in the absence of a clearer public health strategy. Those decisions came as a study from Israel found that although a fourth dose of the Pfizer-BioNTech vaccine offers protection against serious illness for at least six weeks after the shot, it provides only short-lived protection against infection, which wanes after just four weeks.