New studies back need for booster shots: US

WASHINGTON • The United States Centres for Disease Control and Prevention (CDC) released three studies on Wednesday that federal officials said provided evidence that booster shots of the Pfizer-BioNTech and Moderna coronavirus vaccines would be needed in the coming months.

But some experts said the new research did not back up the decision to recommend booster shots for all Americans.

Taken together, the studies show that although the vaccines remain highly effective against hospitalisations and deaths, the bulwark they provide against infection with the virus has weakened in the past few months.

The finding accords with early data from seven US states, gathered this week by The New York Times, suggesting a rise in breakthrough infections and a smaller increase in hospitalisations among the vaccinated as the Delta variant spread last month.

The decline in effectiveness against infection may result from waning vaccine immunity, a lapse in precautions like wearing masks or the rise of the highly contagious Delta variant, experts said, or a combination of all three.

Surgeon-General Vivek Murthy said at a news briefing on Wednesday: "We are concerned that this pattern of decline we are seeing will continue in the months ahead, which could lead to reduced protection against severe disease, hospitalisation and death."

Citing the data, federal health officials outlined a plan for Americans who received the two vaccines to get booster shots eight months after receiving their second doses, starting from Sept 20.

People who received the Johnson & Johnson vaccine may also require additional doses.

But that vaccine was not rolled out until March this year, and a plan to provide boosters will be made after reviewing new data expected over the next few weeks, officials said.

Some scientists were sceptical of the administration's new initiative. "These data support giving additional doses of vaccine to highly immunocompromised persons and nursing home residents, not to the general public," said Dr Celine Gounder, an infectious disease specialist at Bellevue Hospital Centre and a former adviser on the pandemic to the administration.

Boosters would be warranted only if the vaccines were failing to prevent hospitalisations with Covid-19, she said.

"Feeling sick like a dog and laid up in bed, but not in the hospital with severe Covid-19, is not a good enough reason" for a campaign of booster shots, Dr Gounder said.

"We'll be better protected by vaccinating the unvaccinated here and around the world."

It is unclear whether a third dose would help people who did not produce a robust immune response to the first two doses, said Dr Bill Hanage, a public health researcher at the Harvard T.H. Chan School of Public Health.

The recommendation for boosters may also end up undermining confidence in the vaccines, he warned.

"A third shot will add to scepticism among people yet to receive one dose that the vaccines help them," he said.

Together, the new studies indicate that, overall, vaccines have an effectiveness of roughly 55 per cent against all infections, 80 per cent against symptomatic infection, and 90 per cent or higher against hospitalisation, noted Dr Ellie Murray, a public health expert at Boston University.

"Those numbers are actually very good," Dr Murray said. "The only group that these data would suggest boosters for, to me, is the immunocompromised."

NYTIMES