(Reuters) - A fourth dose of the Pfizer/BioNTech vaccine lowered rates of COVID-19 among the elderly but the protection against infection appeared short-lived, a large study in Israel has found.
The second booster's protection against infection dwindled after four weeks, Israeli researchers note in their study published on Tuesday in the New England Journal of Medicine.
Protection against severe illness did not wane during the six week study period following the dose, but more follow-up study was needed to evaluate its longer-term protection, the researchers said.
The adjusted rate of severe COVID-19 in the fourth week after receipt of the fourth dose was lower by a factor of 3.5 compared with a control group that had received only three shots, the researchers calculate.
The adjusted rate of confirmed infection in the fourth week after receipt of the fourth dose was lower by a factor of 2.0, but protection waned after that.
The study on 1.3 million people aged 60 and older looked at data from the Israeli Ministry of Health database between Jan. 10 and March 2, when the Omicron variant was predominant.
It comes ahead of a meeting by the U.S. Food and Drug Administration on Wednesday to discuss the need for additional boosters, a week after the United States authorised a second booster shot for people aged 50 and older amid a spread of the Omicron sub-variant BA.2.
European health ministers have also urged the bloc's governments to back a fourth dose for people over 60.
In Asia, South Korea started giving out fourth doses of COVID-19 vaccines in February and Singapore has said a second booster dose is planned for those aged 80 and older.
Another study from Israel showed last month that seniors who received a second booster of the Pfizer Inc/BioNTech SE COVID-19 vaccine had a 78% lower mortality rate than those who got just one.
Israel started offering a second booster in January.
SOURCE: https://bit.ly/3r2PGKY NEJM, online April 5, 2022.
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