Israel, which leads the world in vaccinating its population against the coronavirus, has produced some encouraging news: Early results show a significant drop in infection after just one shot of a two-dose vaccine, and better than expected results after both doses.
Public health experts caution that the data, based on the Pfizer-BioNTech vaccine, is preliminary and has not been subjected to clinical trials. Even so, Dr. Anat Ekka Zohar, the vice president of Maccabi Health Services, one of the Israeli health maintenance organizations that released the data, called it “very encouraging.”
In the first early report, Clalit, Israel’s largest health fund, compared 200,000 people aged 60 or over who received a first dose of the vaccine to a matched group of 200,000 who had not been vaccinated yet. It said that 14 to 18 days after their shots, the partly vaccinated patients were 33 percent less likely to be infected.
At about the same time, Maccabi’s research arm said it had found an even larger drop in infections after just one dose: a decrease of about 60 percent, 13 to 21 days after the first shot, in the first 430,000 people to receive it.
Maccabi did not specify an age group or whether it had compared the data with a matched, non-vaccinated cohort.
The Israeli Health Ministry and Maccabi released on Monday new data on people who had received both doses of the vaccine, showing extremely high rates of effectiveness.
The ministry found that of 428,000 Israelis who had received their second doses, only 63, or 0.014 percent, had contracted the virus a week later. Similarly, the Maccabi data showed that more than a week after having received the second dose, only 20 of roughly 128,600 people, about 0.01 percent, had contracted the virus.
In clinical trials, the Pfizer vaccine proved 95 percent effective after two doses in preventing coronavirus infection in people without evidence of previous infection. The Israeli results, if they hold up, suggest the efficacy could be even higher, though rigorous comparisons to unvaccinated people have not yet been published.
Both Clalit and Maccabi warned that their findings were preliminary and said they would soon be followed by more in-depth statistical analysis in peer-reviewed scientific publications.
Israel, where more than 40 percent of the population has already received one dose of the vaccine, has become something of an international test case for vaccination efficacy.