Israel Considers 4th Vaccine Dose, but Some Experts Say It’s Premature.

Some scientists warn that too many shots might actually harm the body’s ability to fight the Covid-19 virus. But Israeli experts say there isn’t time to wait.

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The proposal to give a fourth dose to those most at risk drew criticism from other scientists and medical professionals, who said it was premature and perhaps even counterproductive. Some experts have warned that too many shots eventually may lead to a sort of immune system fatigue, compromising the body’s ability to fight the virus.

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While there is evidence that Omicron, discovered just last month, usually causes milder illness than earlier variants, Israeli officials said that by the time they have clearer information, it might be too late to protect the people most at risk.

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Prof. Hagai Levine, an epidemiologist and chairman of the Israel Association of Public Health Physicians, said that Israel was not seeing a sharp rise in infections yet — daily infections are at around 1,200 a day, down from 11,000 at the peak of the Delta wave in August — and there was no evidence that a fourth shot was needed to prevent severe illness from Omicron.

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Decreasing antibodies over time is natural, he said, and boosting antibodies may have limited benefit.