There hasn’t been enough research on how much protection a fourth dose may offer, medical professionals told CNBC.
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Countries are beginning to offer a fourth dose of the Covid-19 vaccine to vulnerable groups, but medical professionals are unsure if it would benefit the general population.
The US Food and Drug Administration has so far authorized a fourth injection only for people age 50 and older, as well as those who are immunocompromised. And the US Centers for Disease Control and Prevention was skeptical about the need for a fourth dose for healthy adults in the absence of a clearer public health strategy.
Those decisions came as a study from Israel found that although a fourth dose of the Pfizer-BioNTech vaccine offers protection against serious illness for at least six weeks after injection, it provides only short-lived protection against infection, which declines afterward. only four weeks. .
No ‘good evidence’ yet
The medical consensus so far is that there has not been enough research on how much protection a fourth dose can offer.
The World Health Organization has not given an official recommendation on a fourth dose, and “there is no good evidence at this point” that it is beneficial, said WHO chief scientist Soumya Swaminathan.
“What we know from immunology is that if you give it another boost, you’ll see a temporary increase in neutralizing antibodies. But what we’ve also seen is that these neutralizing antibodies will go down pretty quickly,” Swaminathan told CNBC in an interview.
“This happened after the third dose. And it happened again after the fourth dose,” he added.
Paul Goepfert, a professor of medicine at the University of Alabama, echoed that view, saying “a fourth dose doesn’t really do much… I’m not sure we have to go out there and just jump and scream.” that everyone needs to get on board.
Since the Israel study shows that the fourth dose can provide protection against serious illness, countries including Israel, Denmark and Singapore have made a second booster vaccine available to high-risk groups.
“Instead of saying the protection wanes, I’d say this booster effect is strongest shortly after the vaccine was given, but it’s still protective overall,” said Ashley St. John, an associate professor in the School of Medicine. from Duke-NUS.
“Importantly, it did not diminish protection against serious disease, which is the most important effect of vaccination that we aim to achieve,” he added.
Annual booster shots?
Questions are being raised about the need for more booster shots, as the emergence of more Covid variants may require more targeted shots.
White House chief medical adviser Anthony Fauci told NBC News in January that people may need booster shots every one to two years.
However, general vaccination approaches may no longer work.
High-risk groups, such as the elderly, may need an annual vaccine, Swaminathan said. But “it is not clear whether a healthy adult will need a regular annual injection.”
It’s also important to note that current vaccines being given may not work for future variants of Covid-19, he said.
If the virus “changes so much that you need to change the composition of your vaccine, then you won’t need another injection,” Swaminathan added. “The challenge with changing the composition of the vaccine is that you are always catching up.”
Goepfert said “only time will tell” how much longer the population has to get booster shots, but the safest approach would be to “plan a booster every year, and maybe combine it with the flu shot.”
The WHO announced on Tuesday that new weekly Covid deaths had fallen to the lowest level since March 2020.
But the more contagious omicron BA.2 subvariant remains the dominant strain in the United States, accounting for 68.1% of all cases in the country during the week ending April 23, according to CDC data.
Although experts predict that the BA.2 subvariant is unlikely to be more severe than the original omicron strain, it should remain a concern.
“I think the infections will continue … they have taken over most of the country,” Goepfert said. “But in terms of serious infections, I think it will continue to be less and less.”
Patients in places with adequate vaccination coverage would experience only “mild or manageable illness” and this would reduce the “burden on the health care system compared to waves of pre-Covid vaccines,” St. John said.
“Just like studying for an exam, a booster shot can activate the immune system’s memories and increase performance during the actual test,” he added.