Both Pfizer and Moderna are asking the U.S. Food and Drug Administration to allow adults to receive a second COVID-19 booster, as a study downplaying its effectiveness is released.
On Thursday, Moderna announced it has submitted a request to the FDA to allow for an amendment to the emergency use authorization, so those aged 18 and over can receive a fourth shot.
The move follows on from Pfizer and BioNTech, who sought a similar emergency authorization for a second booster shot of their vaccine for adults aged 65 and older.
The requests arrive as a study conducted at the Sheba Medical Centre in Tel Aviv, Israel, found that Israeli healthcare workers who received a fourth shot at the height of the spread of the Omicron variant only received marginally more protection than those who received just three.
The study, published in the New England Journal of Medicine, found that a fourth jab was better suited to prevent serious illness or symptoms of COVID-19, rather than protect against Omicron infection itself.
According to the study, those who received a fourth shot of Pfizer jab were 30 percent less likely to get infected, while the figure was just 18 percent for Moderna.
"Our data provide evidence that a fourth dose of mRNA vaccine is immunogenic, safe, and somewhat efficacious (primarily against symptomatic disease)," the study states.
"A comparison of the initial response to the fourth dose with the peak response to a third dose did not show substantial differences in humoral response or in levels of Omicron-specific neutralizing antibodies."
However, as noted by the Agency France-Presse news agency, the study in Israel was small and was not a randomized trial, meaning caution is necessary when drawing conclusions from it.
The researchers also noted that while a fourth vaccination of healthy young healthcare workers may have only "marginal benefits," older and vulnerable people who are more at risk of serious illness or death from COVID-19 were not assessed.
Dr Julian Tang, a clinical virologist at the University of Leicester, said the findings prove that new vaccines are needed to protect certain groups against different strains of the virus.
"If Omicron continues circulating and we are still using the current first-generation COVID-19 vaccines against it, then I agree with the authors that the benefits to otherwise healthy, younger people will be marginal," Tang told AFP.
"Any fourth dose boosters will be more beneficial to the older and more vulnerable groups."
On Monday, Moderna President Stephen Hoge also told Insider that it would be better for older adults or immunocompromised people to receive a fourth COVID-19 shot than younger people.
"For those who are immunecompromised, those who are older adults, over the age of 50 or at least 65, we want to strongly recommend and encourage [a fourth shot], the same way we do with flu vaccines," he said.
"Is it necessary? I think that's a strong word. I think it will provide a benefit to anyone who gets it," Hoge said.
Speaking to CBS's Face the Nation on Sunday, Pfizer's chief executive, Dr. Albert Bourla, said he believes it is "necessary" for older or high risk people to receive a fourth shot due to waning protection from the third dose.
"The protection that you are getting from the third, it is good enough, actually quite good for hospitalizations and deaths," he said. "It's not that good against infections."
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Newsweek is committed to challenging conventional wisdom and finding connections in the search for common ground.
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Ewan Palmer is a Newsweek News Reporter based in London, U.K. His focus is reporting on US politics, domestic policy ... Read more
