Pfizer said Thursday that the Covid-19 vaccine blocked 94% of asymptomatic infections in an Israeli study – a result that CEO Albert Bourla called “extremely important.”
The study, which measured results two weeks after the second dose, also found the vaccine to be at least 97% effective against symptomatic Covid cases, hospitalizations and deaths, said Pfizer, who developed the BioNTech injection.
The analysis used data collected between January 17 and March 6, when the Pfizer vaccine was the only available injection in the country and when the more transmissible B.1.1.7 variant from the UK was the dominant strain.
“This is extremely important … to society,” Bourla said in an interview with CNBC’s “Squawk Box.” “The asymptomatic carriers and patients are the ones who mainly spread the disease. We expected something good in terms of being symptomatic,” he said, adding that the company was not expecting such a “high number” of asymptomatic cases.
An asymptomatic person is someone who has Covid-19 but has no symptoms and never develops them. It is not the same as a presymptomatic patient who later develops symptoms. According to a study in JAMA published in January, it is estimated that at least 50% of transmission comes from people who have no symptoms.
The Israeli study means the Pfizer vaccine could significantly reduce transmission.
“This clearly demonstrates the power of the COVID-19 vaccine to combat this virus and encourages us to continue our vaccination campaign even more intensively,” said Yeheskel Levy, director of the Israeli Ministry of Health in a press release. We are striving for even greater absorption among people of all ages, which gives us the hope of regaining normal economic and social function in the not-so-distant future. “
Israel launched its national vaccination campaign in December, prioritizing people over 60, health workers and those with comorbid conditions. In February it was the world leader in vaccinations, vaccinating millions of citizens against the virus.
In January, Pfizer and the Israeli Ministry of Health entered into a partnership agreement to monitor the real impact of their vaccine.
Bourla also said Thursday that the company is assessing the impact a booster dose could have on the virus, particularly the B.1.351 strain in South Africa, which he says “appears to be the toughest.”
“We already have very good protection with two doses,” he said.