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- A third dose of Pfizer’s coronavirus vaccine dramatically reduces the risk of infection and serious illness in the elderly, according to a new study.
- A team of researchers in Israel published the results Wednesday in the New England Journal of Medicine.
- Still, one expert urged caution in interpreting the results, saying the study has major limitations.
Seniors in Israel who received a booster of Pfizer’s coronavirus vaccine were much less likely to be infected or develop serious illness, a massive study released Wednesday found.
Including more than 1.1 million people aged 60 and over, the study examined thousands of infections and hundreds of cases of serious illness, providing some of the most compelling evidence to date on the value of injections. reminder.
Israel began offering booster doses to its elderly population on July 30, and a group of researchers analyzed national health records through August.
Israeli study shows boosters reduce risk of infection and severe cases of COVID-19
The main finding was that the older population, when boosted, was 11 times less likely to be infected and 19.5 times less likely to get seriously ill compared to similar people who received two doses but no booster. .
The study is likely to be influential, as its publication comes just two days before the Food and Drug Administration convenes an independent panel of experts to discuss Pfizer’s request for booster shots in the United States. . Israeli health officials are due to present the results of their booster campaign at that meeting on Friday, and U.S. health officials have pointed to Israel’s experience to strengthen their argument for the booster injections.
The Biden administration has previously said it plans to start offering booster shots to the general public on September 20, based on clearances from the FDA and the Centers for Disease Control and Prevention.
In the Israeli study, the group that did not receive a booster recorded 4,439 infections and 294 serious illnesses. The booster group had 934 infections and 29 severe cases. The risk reduction rates explained the fact that the two groups were not of equal size, as many more people joined the booster group over time.
Data should be viewed with caution
The result that the booster shots reduced the risk of serious illness by nearly 20 times is surprising and should be viewed with some skepticism, said Ellie Murray, an epidemiologist at Boston University.
The study has major limitations, she said. Specifically, the researchers observed the real world, rather than testing a booster under more controlled conditions. This means that there are many factors that can skew the results.
For example, the group of people who are the first to be boosted may be more careful with other virus prevention methods, such as masking or social distancing. They might be less likely to get infected for these reasons, instead.
In addition, the study has a very limited follow-up time and does not show how long protection against boosters can last. This is a critical question in determining whether a recall campaign is worth launching.
The limited duration of the study may distort its conclusions. Researchers only started counting cases for the booster group when they were 12 days away from the third dose.
It can take up to a month on average for a person to go from exposure to infection to serious illness, Murray said. Therefore, the study may not include enough follow-up time to show the true effect of the boosters.
There are no high quality studies of booster injections.
“It’s not clear to me that there is enough follow-up time, even for the first few boosters,” Murray said.
“All of these issues together make it very difficult to know how much we can trust the number that emerges from the study,” added Murray.
The larger challenge is that there is an absence of high-quality data that provides better answers to these questions. Leading vaccine developers don’t conduct randomized controlled trials to test booster doses against a placebo and see which group does best in the long term. Instead, the drugmakers conducted small studies, stimulating a few hundred people and finding a high immune response, which may suggest but not prove better protection, especially against serious illness.
Israeli researchers have attempted to account for a number of potential confounding factors, including demographic differences between boosted and unboosted populations in Israel. They analyzed the data with several techniques that produced slightly different numbers but the same overall result: a massive reduction in the risk of infection, ranging between 10 and 13 times lower for the boosted population, depending on the analysis performed.
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