evidence: The US Food and Drug Administration on Wednesday authorized updated Covid-19 vaccine booster shots from Moderna and Pfizer. This is the first time updated Covid-19 vaccines have received emergency use authorization in the United States. [...] On Wednesday, FDA officials defended their swift emergency use authorization of the updated Covid vaccine booster. Pfizer and Moderna submitted for authorization last week. [...] This is similar to the way annual flu vaccines are tested each year, but it’s a first for Covid-19 vaccines. The approach has generated some controversy among vaccine experts. In making the authorization, the agency did not call a new meeting of its independent vaccine advisers, who often weigh in on vaccine changes; the advisory group had offered its insight on updating the original vaccine in meetings over the summer.