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August 23, 2021

Do Covid-19 'booster' shots really work? Here's what early data shows.

Daily Briefing

    As Israel faces a surge in Covid-19 cases due to the delta variant, data from the Israeli Health Ministry shows that a third dose of Pfizer-BioNTech's Covid-19 vaccine significantly improved protection against hospitalization or serious disease.


    The rollout of Covid-19 vaccines in Israel was one of the fastest and most comprehensive in the world. By March 25, more than half of Israel's population was fully vaccinated, and by June, the country had lifted all coronavirus-related restrictions.

    However, in the summer, Israel saw a surge in Covid-19 cases, which experts believe was fueled by two factors: waning protection from the vaccine and the spread of the highly contagious delta variant.

    "The most influential event was so many people who went abroad in the summer—vacations—and brought the delta variant very, very quickly to Israel," Siegal Sadetzki, a former public health director in Israel, said.

    Even so, the rate of severe Covid-19 cases among the vaccinated remains low. As of Thursday, according to data from the Health Ministry, the rate of severe Covid-19 cases was nine times higher among unvaccinated people over the age of 60 than among vaccinated people in the same age range.

    Similarly, the rate of severe Covid-19 cases among unvaccinated people under 60 was about twice the rate of severe cases among vaccinated people under 60.

    But because so many people in the country have been vaccinated, even a low rate of severe breakthrough infections has led to a significant surge in hospitalizations. NPR reports that half of the seriously ill patients in Israel hospitalized with Covid-19 had been fully vaccinated at least five months ago, and the majority of them are over the age of 60 with comorbidities.

    Data shows booster shots provide significantly increased protection

    On July 30, Israel began administering booster shots of the Pfizer-BioNTech vaccine to those over the age of 60. On Thursday, the country dropped that age eligibility to 40.

    Data from the Health Ministry indicate that a third dose of the Pfizer-BioNTech vaccine provided four times the protection against infection as two doses in people aged 60 and over, Reuters reports. (According to Reuters and NPR, the findings are similar to data released by Israel's HMO Maccabi Healthcare Services last week, which found that among 149,144 people, a third Pfizer shot among recipients above age 60 reduced the odds of infections by 86% and cut the risk of severe infection by 92%.)

    Similarly, a third dose offered about five to six times the protection of two doses against serious illness and hospitalization in people aged 60 and over, according to the Health Ministry data.

    According to Reuters, the data underlying these figures was presented at a health ministry panel meeting on Thursday and later published on the ministry's website. Full details of the study, however, still have not been released.

    The debate over booster shots continues

    The news comes as experts in the United States continue their debate over the necessity of booster shots. On Wednesday, the Biden administration announced that Americans who had received an mRNA vaccine would be able to get a booster shot beginning in September, pending approval by FDA and a recommendation by CDC.

    However, health experts are divided on whether booster shots are necessary, a debate that prompted CDC's Advisory Committee for Immunization Practices (ACIP) to push back its meeting to discuss booster shots by one week, Bloomberg reports.

    "The data [is] coming in rapidly, and we want to make sure we follow our process for review and to ensure we can have a robust deliberation at the next open meeting," Grace Lee, chair of ACIP, said.

    Joshua Barocas, associate professor of medicine at the University of Colorado, said he believes the "federal government is simply trying to stay ahead of the curve." However, Barocas said, "I have not seen robust data yet to suggest that it is better to boost Americans who have gotten two vaccines than invest resources and time in getting unvaccinated people across the world vaccinated."

    The World Health Organization has also called for wealthier countries to not offer booster shots to their population and instead help poorer countries get vaccinated.

    Surgeon General Vivek Murthy said the United States' efforts to provide boosters to its population won't interfere with efforts to provide other countries with shots.

    "We have to protect American lives and we have to help vaccinate the world, because that is the only way this pandemic ends," Murthy said.

    He did acknowledge that providing booster shots to Americans could "take away" from the supply of vaccines for the rest of the world, but added that the United States has been working to improve the global vaccine supply and production recently to make sure that doesn't happen.

    "We don't have a choice," Murthy said. "We have to do both." (Estrin, "Goats and Soda," NPR, 8/20; Ray, Forbes, 8/23; Reuters, 8/22; Suliman et al., Washington Post, 8/23; Anderson, Becker's Hospital Review, 8/20; Pradhan, Kaiser Health News/Modern Healthcare, 8/20; Saric, Axios, 8/22)

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