The U.S. authorized the first major makeover of the Covid-19 vaccines this week in an effort to stem an expected tide of infections and hospitalizations this fall.
But it’s unclear how much protection the new booster shots will provide. The Food and Drug Administration and the Centers for Disease Control and Prevention cleared the shots without any data from clinical trials that are testing the reformulated doses in humans. The new boosters, authorized for people ages 12 and older, target the highly contagious and immune-evasive omicron BA.5 subvariant that has caused a wave of breakthrough infections over the summer. The shots also target the original strain of the virus that first emerged in Wuhan, China, in 2019.
The nation’s top health officials acted with urgency this summer to ensure the new boosters would roll out in time for the fall. They are worried that the waning effectiveness of the old vaccines is creating an opening for omicron to cause another wave of hospitalizations this winter as people spend more time indoors where the airborne virus spreads more easily.