RELATED: Dr. Fauci Says Doing This Could “Defeat the Purpose” of Your Booster. A study published Sept. 15 in The New England Journal of Medicine found that older adults who received a Pfizer booster shot were significantly less likely to develop a severe case of COVID. The study included more than 1.1 million people 60 years and older in Israel, where booster doses for older adults have been available since the end of July. According to the study, people in this age group were nearly 20 times less likely to develop severe illness from COVID if they received an additional Pfizer shot compared to fully vaccinated individuals of the same age who had only gotten two doses. The researchers also found that the rate of infection was around 11 times lower among the boosted group. “Israel has clearly demonstrated that, in the face of waning immunity, a booster (third dose) program can be implemented safely at a national level and that a booster dose of [Pfizer] is an effective strategy to restore high levels of protection against COVID-19 outcomes (i.e., back to roughly 95 percent) in a period when Delta is the dominant strain,” Pfizer stated in a report released Sept. 15 by the U.S. Food and Drug Administration (FDA), citing the Israel study. RELATED: For more up-to-date information, sign up for our daily newsletter. At the same time, some officials warn against taking the results of this study at face value. Ellie Murray, ScD, an epidemiologist at Boston University, told Business Insider that the results should be viewed with some skepticism, as the study had major limitations, like the fact that the Israeli researchers observed real-world data, rather than testing the booster in a study with controlled conditions.ae0fcc31ae342fd3a1346ebb1f342fcb Murray also questioned the time frame of the study, which had a limited follow-up time. The researchers included people who had received booster doses 12 days prior, while it can take up to a month on average for an individual to go from being exposed to COVID to infected and then severely ill, according to Murray. This makes it hard to show the true effect of the boosters, as well as to determine how long protection from boosters may actually last over time. “It’s not clear to me that there’s anywhere near enough follow-up time, even for the earliest boosters,” Murray said. “All of these problems together make it really hard to know how much we can trust that number that comes out of the study.” RELATED: Dr. Fauci Warns Not to Do This If You Got Pfizer.