US plans for booster shots a year after inoculation

WASHINGTON • The United States is preparing for the possibility that a booster shot will be needed between nine and 12 months after people are initially vaccinated against Covid-19, a White House official said.

While the duration of immunity after vaccination is being studied, booster vaccines could be needed, Dr David Kessler, chief science officer for US President Joe Biden's Covid-19 response task force, told a congressional committee meeting on Thursday.

"The current thinking is those who are more vulnerable will have to go first," he said.

"We are studying the durability of the antibody response. It seems strong, but there is some waning of that, and no doubt the variants challenge. I think for planning purposes, we should expect that we may have to boost (immunity with further vaccinations)."

Meanwhile, Pfizer chief executive Albert Bourla said people will likely need a third booster dose of Covid-19 vaccine within 12 months, and could need annual shots, CNBC reported, based on his comments from April 1, which were made public on Thursday.

"We need to see what would be the sequence, and for how often we need to do that, that remains to be seen," said Dr Bourla.

"A likely scenario is that there will be likely a need for a third dose, somewhere between six and 12 months, and then from there, there will be an annual revaccination, but all of that needs to be confirmed."

He said Covid-19 variants will play a key role, adding that "it is extremely important to suppress the pool of people who can be susceptible to the virus".

Initial data has shown that vaccines from Moderna and partners Pfizer and BioNTech retain most of their effectiveness for at least six months, though for how much longer has not been determined.

Even if that protection lasts far longer than six months, experts have said that rapidly spreading variants of the coronavirus and others that may emerge could lead to the need for regular booster shots, similar to annual flu shots.

The US is also tracking infections in people who have been fully vaccinated, Dr Rochelle Walensky, director of the US Centres for Disease Control and Prevention, told the House sub-committee hearing.

Of 77 million people vaccinated in the US, there have been 5,800 such breakthrough infections, Dr Walensky said, including 396 people who required hospitalisation and 74 who died.

She added that some of these infections occurred because the vaccinated person did not mount a strong immune response.

However, the concern is that in some cases, they are occurring in people infected by more contagious virus variants.

Earlier this month, Pfizer and BioNTech said their vaccine is around 91 per cent effective in preventing Covid-19, and more than 95 per cent effective against severe cases of Covid-19 up to six months after the second dose.

In their findings, they cited updated trial data that included more than 12,000 people fully inoculated for at least half a year.

Researchers say more data is needed to determine whether that protection lasts.

The Pfizer vaccine, developed in partnership with German firm BioNTech, currently plays a leading role in American and European vaccination campaigns.

The US pharmaceutical giant announced in February that it was testing a third dose of its vaccine to better combat the emerging variants.

REUTERS, AGENCE FRANCE-PRESSE