Early data from Israel suggests Covid-19 infection rates began to decrease among a group of vaccine (疫苗) recipients two weeks after they received the first shot of Pfizer Inc. and BioNTech SE's vaccine, offering important insights to other countries as they roll out their own campaigns.
The small country — whose roughly nine million population is about the size of New York City's — has vaccinated nearly a fourth of its population in just under a month, the first country to hit that mark as it fights an upsurge (激增) in new infections.
Israel's largest health-care provider, Clalit Health Services, compared test positivity rates among 200, 000 people over 60 who received the vaccine with 200, 000 that didn't. Until day 14, there was little difference between the two groups. But after that, the data showed a 33% fall in infection rates among those who had already been vaccinated compared with those who hadn't. Clalit noted that the number of people infected was statistically significant, but said it wouldn't release final numbers until its study is published.
Pfizer says people must receive both doses of the vaccine for it to be fully effective. In Pfizer's trials, the vaccine was shown to take about 12 days before it started to protect people. The Clalit study suggests that the first dose could reduce infections among those vaccinated as early as two weeks after injection.
Israel, like many other countries, has given priority to those over 60 in the first stage of its vaccination drive, making the group the best fit for study. Nearly three out of four people in this age group have received the first dose of the vaccine since Israel's campaign began on Dec.20.
Israel has committed to providing Pfizer with real-time data about their vaccine, from effectiveness to side effects, which Israeli officials said helped it obtain early supply from the vaccine maker. Separately, Israel's Health Ministry published data about side effects from the vaccine, saying they were similar in frequency and character to other vaccinations given to its people.
