Starting this week, some at-risk Americans become eligible for fourth Covid-19 shot

Immunocompromised people in the US can receive a booster shot - a fourth dose of the Pfizer-BioNTech or Moderna vaccine - five months after their third dose. PHOTO: AFP

NEW YORK (NYTIMES) - Some people with a weakened immune system can get a fourth dose of a Covid-19 vaccine as early as this coming week, according to new recommendations from the Centres for Disease Control and Prevention (CDC).

The CDC endorsed a third dose of the Pfizer-BioNTech or Moderna vaccine for moderately or severely immunocompromised people on Aug 13 but said this would be considered a part of the primary immunisation, not a booster shot.

In October, the agency said those immunocompromised people could receive a booster shot - a fourth dose of vaccine - six months after their third dose. These guidelines were consistent with its recommendation for other adults.

Last week, hoping to stem the surge of infections due to the highly contagious Omicron variant, the CDC shortened that interval to five months for a booster shot for Pfizer-BioNTech or Moderna recipients.

For immunocompromised people who received a single shot of the Covid-19 vaccine made by Johnson & Johnson, the CDC does not recommend additional primary doses, but advises that they get a booster shot of the Pfizer-BioNTech or Moderna vaccine two months after the first dose.

Some people are born with absent or faulty immune systems, and in others, treatments for some diseases such as cancer diminish the potency of immune defences. The CDC estimates there are about seven million immunocompromised individuals in the country.

Many of them produce few to no antibodies in response to a vaccine or an infection, leaving them susceptible to the virus. When they do become infected, they may suffer prolonged illness, with death rates as high as 55 per cent.

It is unclear what proportion of those people are protected by additional doses. Still, with the Omicron variant surging in the country, some immunocompromised people sought out fourth or even fifth shots of the vaccines even before the CDC changed its guidelines.

Although receiving multiple doses of vaccines in a short period is unlikely to be harmful, it may produce diminishing returns, according to some experts.

The CDC has said that any American 12 and older can receive a Pfizer-BioNTech booster - those 18 and older can alternatively receive a Moderna booster - five months after completing their initial shots with those vaccines.

Israel has already begun offering fourth doses to high-risk groups, including older adults.

But the Biden administration has not yet said whether it plans to follow suit.

Asked on Friday (Jan 7) about the possibility of a fourth shot for the general population, Dr Rochelle Walensky, director of the CDC, said that the focus remained on Americans eligible for their third shots.

She added that US officials remained in close touch with Israel experts about their data.

"We will be following our own data carefully as well to see how these boosters are working in terms of waning effectiveness, not just for infection but, importantly, for severe disease," she said.

Join ST's Telegram channel and get the latest breaking news delivered to you.