Pfizer/BioNTech say data suggests vaccine 94% effective in preventing asymptomatic infection

Pfizer Inc and BioNTech SE said on Wednesday that real-world data from Israel suggests their Covid-19 vaccine is 94% effective in preventing asymptomatic infections, meaning it could significantly reduce transmission.

The companies also said the latest analysis of the Israeli data shows the vaccine was 97% effective in preventing symptomatic disease, severe disease and death. That is basically in line with the 95% efficacy Pfizer and BioNTech reported from the vaccine's late-stage clinical trial in December.

Israel's Health Ministry, which has been sending data to Pfizer and is working with the healthcare providers giving the vaccine, did not respond to requests for comment.

The analysis also shows real-world evidence of the vaccine's effectiveness against a highly infectious variant of Covid-19 first discovered in Britain, known as B.1.1.7. More than 80% of the tested specimens when the analysis was conducted were variant B.1.1.7.

There were only a limited number of infections in Israel caused by the so-called South African variant - known as B.1.351 - so they were not able to evaluate effectiveness against this variant.

In terms of population covered, Israel is leading the world in its vaccination programme, thanks in part to an agreement to share data with Pfizer and BioNTech.

As of Wednesday, around 55% of Israel's 9 million population had been given at least one dose of the Pfizer/BioNTech Covid-19 vaccine, according to Health Ministry data, and 43% have received both doses.

Since the mid-January peak, Israel has seen 71% fewer Covid-19 deaths, 55% fewer cases, 45% fewer new critically ill patients and 40% fewer critically ill patients in hospitals, according to Eran Segal, a data scientist at the Weizmann Institute of Science.

On Wednesday, 2,802 Israelis tested positive -- or 2.9% from nearly 99,000 tests.

According to the analysis, unvaccinated individuals were 44 times more likely to develop symptomatic Covid-19 and 29 times more likely to die from Covid-19 than those who had received the vaccine.

The data, collected from Jan. 17 to March 6, has not yet been peer reviewed.

Israel's Health Ministry previously found that the Pfizer vaccine developed with Germany's BioNTech reduces infection, including in asymptomatic cases, by 89.4% and in symptomatic cases by 93.7%. That was in data collected from Jan. 17 to Feb. 6.

Pfizer did not provide further details on its analysis of asymptomatic infections. In a previous unpublished study by the health ministry and Pfizer, Israeli researchers said further study was needed on asymptomatic transmission among people fully vaccinated because they are less likely in Israel to be tested for Covid-19.