US plans to offer second booster to older people

WASHINGTON • The Biden administration is planning to give Americans aged 50 or older the option of a second booster of the Pfizer or Moderna coronavirus vaccine without recommending outright that they get one, according to several people familiar with the plan.

Major uncertainties have complicated the decision, including how long the protection from a second booster would last.

Much depends on when the next wave of Covid-19 infections will hit, and how hard. Should the United States be hit by a virulent surge in the next few months, offering a second booster now for older Americans could save thousands of lives.

But if no major wave hits until autumn, extra shots now could turn out to be a questionable move that wastes doses and sows doubt about the government's strategy.

The Food and Drug Administration could authorise a second booster early this week, said people familiar with the deliberations. The Centres for Disease Control and Prevention would then follow with its own advice.

In Australia, the authorities on Friday said they would roll out a fourth dose of Covid-19 vaccines to the most vulnerable population starting next month.

The decision came amid a steady rise in cases fuelled by the highly contagious BA.2 sub-variant of the Omicron strain and concerns of co-circulation of Covid-19 and flu viruses during colder months as most social distancing restrictions end. Australia's winter runs from June to August.

A second booster will be offered from April 4 to those who had their previous booster shot at least four months ago and are over 65 years old, indigenous Australians aged over 50, people with disability or severely immunocompromised, Health Minister Greg Hunt said.

Moderna this month sought emergency use authorisation from the US authorities for a second booster shot for all adults. That request came just days after Pfizer-BioNTech filed for similar authorisation for its own second booster for people aged 65 and older.

One reason older adults may benefit from an additional booster shot is that as the immune system ages, it tends to weaken and does not produce the same quantity or quality of antibodies as it did when it was younger.

On top of that, older adults often have other medical conditions that take up the body's attention, putting them at higher risk of severe disease, said Dr Christian Gaebler, an immunology researcher at Rockefeller University in New York City. "Diabetes, hypertension, obesity and chronic kidney disease are all risk factors for severe Covid-19," he said. "And we know that these usually manifest in older age."

To justify second boosters for people 65 and above, Pfizer-BioNTech relied heavily on evidence from two studies done in Israel that suggested that people who had received fourth shots were less likely to become infected with the virus compared with those who had received three doses.

In one study, published in February, scientists reviewed the health records of about 1.1 million people aged over 60 who had received a fourth dose and compared them with those who had received just three doses. They found that the rate of confirmed infections, as well as that of severe illness, was lower in people who had gotten their fourth shot.

The second study, published last Wednesday in The New England Journal of Medicine, looked at Israeli healthcare workers of all ages and found that fourth shots from both Pfizer and Moderna vaccines bolstered antibody levels, though they were not very good at preventing infection.

Experts cautioned that the available data is still preliminary and has not yet shown how long the benefits of a fourth dose will last.

They also argue that the existing coronavirus vaccines need to be modified because the virus' variants are diminishing their power. More than a dozen studies are under way to find the next generation of vaccines, with the first results expected in May or June. If all goes well, that would allow enough time to produce new doses before autumn.

NYTIMES, REUTERS