In a nod to the ongoing risk the coronavirus poses to millions of Americans, the Centres for Disease Control and Prevention (CDC) recommended on Wednesday that adults 65 and older and those with weakened immune systems receive another dose of the reformulated booster that debuted last fall.
The endorsement followed a day-long discussion by the CDC's expert advisers. The Food and Drug Administration (FDA) authorised the booster plan Tuesday, and the CDC's recommendation was the final administrative step. Eligible Americans will be able to receive booster doses immediately.
And instead of needing an initial series of two shots, unvaccinated people will now require just a single dose of the reformulated, or “bivalent,” Covid-19 shot to be considered vaccinated.
Until now, federal officials had required two doses of the older vaccine before recipients could begin to receive the bivalent boosters, a process some experts felt was confusing.
Limited data on the reformulated vaccines indicate that in older adults, the shots offer additional protection against severe disease and death from Covid-19, although the protection wanes rapidly in the weeks after inoculation.
There are about 53 million adults 65 and older in the United States, accounting for about 16 per cent of the population, according to the Census Bureau. And 7 million Americans have weak immune systems because of an illness or a medication.
Roughly 250 people in the United States are still dying from Covid-related causes each day, a vast majority of whom are over 70 or have impaired immune systems. The median age of those hospitalised is 75, according to the CDC.
Yet only about 43 per cent of adults 65 and older have received a bivalent booster shot.
By this point, most Americans have built up some immunity against the virus, whether through prior infections, vaccinations or both. The new guidelines acknowledge as much, but allow for those still at high risk from the virus to protect themselves, and to do so free of charge.
“The one-size-fits-all policy was simple but not optimal,” said Dr Jeremy Faust, an emergency medicine physician and health policy expert at Brigham and Women's Hospital in boston. “The new regimen acknowledges that there's now an extraordinary spectrum of Covid-19 risk, from mild to massive, depending on who you are.”
People who are severely immunocompromised, such as organ transplant recipients, may want to opt for booster shots every six months or even more frequently, Dr Faust said.
The new guidelines come weeks after Britain and Canada recommended additional shots for older adults and immunocompromised people. (Britain recommended the shots for those 75 and older and Canada only for those 80 and older.)
The CDC now says that adults 65 and older may opt for another dose of the bivalent vaccine at least four months after their first shot.