Pfizer CEO Albert Bourla has told CBS television that a fourth dose of his COVID-19 vaccine is likely to be necessary to achieve greater protection against the disease, especially now that more contagious variants such as omicron However, an Israeli study has found that this second booster vaccine may only provide marginal benefits over omicron.
The research, published in the New England Journal of Medicine, has analyzed the immunogenicity and safety of a fourth dose of the Pfizer-BioNTech and Moderna mRNA-type COVID-19 vaccines in a group of 270 workers at the Center Sheba doctor in Tel Aviv, Israel, who received a fourth dose four months after the third injection.
The results showed that a second booster dose was safe and had the ability to increase neutralizing antibodies – which prevent SARS-CoV-2 from infecting cells – to levels similar to those observed after the third dose, just before the protection began to decline over time.
However, what most caught the researchers’ attention was that they found that the fourth dose against COVID-19 did not provide much additional protection against the omicron variant. Specifically, they observed that those who received the fourth Pfizer injection had a 30% lower risk of contracting the infection than those who had three doses, a percentage that dropped to 18% in the case of those who had received the Moderna vaccine.
Low efficacy of the fourth dose in health workers
The protection afforded by a fourth dose against infection with symptoms was slightly better in participants under 40 who received a fourth injection, 43% for Pfizer and 31% for Moderna, compared to people who received three vaccines. Even so, the results must be interpreted with caution, since it is a non-randomized study and with a small group of people.
Those who received the fourth dose from Pfizer had a 30% lower risk of COVID-19 than those who had three doses, and 18% in the case of those from Moderna
The authors indicate that they believe that the benefits of the three doses that have been administered so far against the original strain had reached their maximum immune response, so that with the boosters they only managed to restore the diminished immunity, instead of increasing it completely. .
“Furthermore, we observed low vaccine efficacy against infections in healthcare workers, as well as relatively high viral loads suggesting that those who were infected were infectious. Therefore, a fourth vaccination of young, healthy health workers might have only marginal benefits,” the researchers, led by Gili Regev-Yochay, stated.
Therefore, their assessment shows that it is important to continue researching a specific vaccine for omicron, which would be more effective for young and healthy people. On the other hand, they indicate that a fourth dose would be more beneficial for older groups and for those who are vulnerable due to illness or a depressed immune system.
“Ideally, we need new COVID-19 vaccines designed specifically against omicron if we want to improve this protection for the most vulnerable, in the same way that we update the seasonal flu vaccine every year, to ensure the best possible combination against the strain of virus that we have. currently circulating”, they conclude.
.
