Pfizer said Thursday its Covid-19 vaccine blocked 94% of asymptomatic infections in an Israeli study – a finding that CEO Albert Bourla described as “extremely important”.
The study, which measured results two weeks after the second dose, also found that the vaccine was at least 97% effective against symptomatic Covid cases, hospitalizations and deaths, according to Pfizer, who developed the shot with BioNTech.
The analysis used data collected between January 17 and March 6, when Pfizer’s vaccine was the only available shot in the country and the more transmissible variant B.1.1.7 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 primarily spread the disease. We expected something good in terms of symptoms,” he said, adding the company did not expect 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 pre-symptomatic patient who develops symptoms later. According to a study published in JAMA in January, it was estimated that at least 50% of transmission was from people with no symptoms.
The Israeli study means the Pfizer vaccine could significantly reduce transmission.
“This clearly shows the power of the COVID-19 vaccine to fight 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 acceptance among people of all ages, which gives us hope that we will be able to return to normal economic and social functions in the not too distant future.”
Israel launched its national vaccination campaign in December, prioritizing people aged 60 and over, healthcare workers, and people with comorbid illnesses. By February, it was the world leader in vaccinations, vaccinating millions of its citizens against the virus.
In January, Pfizer and the Israeli Ministry of Health signed a collaboration agreement to monitor the real effects of its vaccine.
Bourla also said the company on Thursday was assessing the effects of a booster dose on the virus, particularly the B.1.351 strain in South Africa, which “appears to be the toughest”.
“We already have very good protection with two doses,” he said.
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