Israel's Health Chiefs Fear Vaccine's Effectiveness Against Delta Lower Than Reported

An epidemiological institute's preliminary figures suggest this might be the case, though the percentages could be skewed because of heavy testing in hot spots

Ido Efrati
Ido Efrati
A woman receiving a coronavirus test in Tel Aviv on Sunday.
A woman receiving a coronavirus test in Tel Aviv on Sunday. Credit: Moti Milrod
Ido Efrati
Ido Efrati

Based on the latest data, the Health Ministry fears that the coronavirus vaccine’s effectiveness against the delta variant may be even lower than the ministry's numbers showed two weeks ago.

Back then, the ministry said the vaccine was 64 percent effective in preventing infection and 93 percent effective in preventing serious illness. But figures presented Sunday evening to the coronavirus task force indicate that both numbers were too high.

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The Gertner Institute, which studies epidemiology and health policy, has been analyzing the ministry’s data, though the researchers haven’t yet finished their analysis.

The picture thus could still change, but if the figures presented Sunday prove accurate, there is real cause for concern, according to a person present at the task force meeting.

“I hope it turns out that the findings are the result of sampling verified patients in outbreak locales that had high vaccination rates, which would slant the picture, rather than being a nationwide picture,” he said. “In the coming days, the Health Ministry is due to release the data after the analysis has been completed.”

When the ministry announced two weeks ago that the vaccine was just 64 percent effective at preventing infection with delta – a much lower success rate than was found in Britain – many Israeli experts guessed that the result stemmed from a methodological error. Later, the ministry published its methodology.

The ministry fears that the vaccine’s effectiveness has eroded both because delta is better than previous variants at breaking through the vaccine's immune protection and because the effectiveness wanes as time passes since the two shots.

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