Fourth COVID Shot Triples Protection From Serious Illness, New Israeli Data Shows

A new large-scale study of Israeli vaccine data has confirmed that a fourth COVID-19 vaccine dose roughly triples protection from severe complications in people over 60 versus those who received only three doses in that age group.

The study, conducted by a team of researchers from several Israeli institutions and published in the peer-reviewed New England Journal of Medicine, reviewed data from more than one million people in Israel over the age of 60 who were eligible for a fourth vaccine dose between January and February of this year. Among those who received a fourth dose, severe illness – that requiring hospitalization – was about three times lower than in those who only received three doses.

The study dovetails with data from Israel's Health Ministry earlier this year, which also showed that people over 60 in Israel reaped these same benefits from a fourth vaccine dose. That study was based on statistics on some 400,000 people who had received a fourth shot and 600,000 who had received a third shot.

The Health Ministry's study also found that three shots of the Pfizer and Moderna vaccines were about 67 percent effective against omicron-related symptomatic disease compared with unvaccinated people. Two doses offered no significant protection against omicron, the researchers found.

The more recent study also found that a fourth vaccine dose produced a twice-lower rate of verified COVID cases, although that protection faded over the eight-week study.

These studies echo previous research – including studies in the U.S., Germany, South Africa and the U.K. – indicating available vaccines are less effective against omicron than earlier versions of the coronavirus, but also that boosters significantly improve protection.

This also comes as the number of serious coronavirus cases in Israel fell to a nearly three-month low on Monday, and spread looks to be shrinking according to the R number, which represents the average number of people each coronavirus carrier infects. An R number under 1 indicates receding spread, and it fell to 0.92 as of March 24, the most recent data available.

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These developments are adding to hopes that Israel has managed to avoid another major wave of COVID infection fueled by the omicron variant BA.2.