Clalit, the country’s largest healthcare provider, said the same group was also 92 per cent less likely to develop severe illness from the virus. The comparison was against a group of the same size, with matching medical histories, who had not received the vaccine.
Symptomatic infections of Covid-19 dropped by 94 per cent in 600,000 people who received two doses of the Pfizer/BioNTech vaccine, a major “real world” study conducted in Israel has shown.
Clalit’s controlled study, which covered a total of 1.2 million people, is the first of its kind and confirms the findings of the clinical study conducted by Pfizer last year.
“It shows unequivocally that Pfizer’s coronavirus vaccine is extremely effective in the real world a week after the second dose, just as it was found to be in the clinical study,” said Ran Balicer, Clalit’s chief innovation officer.
He added that the data indicates the Pfizer vaccine, which was developed in partnership with Germany’s BioNTech, is even more effective two weeks or more after the second shot.
Clalit, which provides health care to more than half of Israel’s population, reported high vaccine efficacy of 91 to 99 per cent over a period of seven days or more after participants had received a second dose of vaccine.
Professor Ran Blitzer, director of the Clalit Research Institute, said: “The trends we identify indicate that continued follow-up for additional weeks after the second dose will significantly increase the measured efficacy of the vaccine.
“In fact, in a preliminary examination, we identify even higher efficacy for the prevention of symptomatic and severe disease among the vaccinated after 14 days”.
The full results from Clalit’s study are expected to be published in the coming weeks, and are due to include findings on the extent to which the Pfizer vaccine blocks transmission of the virus.
Explaining how the study was run, Clalit said that “each vaccinated person was tested in relation to an unvaccinated person similar to him in a long series of indicators such as risk level of infection, level of risk of developing serious disease, health status and more.
“The creation of the control group was done dynamically so that people were deducted and moved between the groups if their immunisation status changed over time.
“This form of calculation, which produces a complete resemblance in time to the place and personal characteristics between the vaccinated and non-vaccinated at any given moment, allows to fully normalise the impact of events that happened in parallel – such as the effect of quarantine, and changing vaccine contraindications”.
Israel has begun easing its third lockdown but the further lifting of restrictions will only be allowed on the conditions that at least three million Israelis have received their second vaccine shot.
Researchers at the Weizmann Institute of Science, who have been tabulating national data, said on Sunday that a sharp decline in hospitalisation and serious illness identified earlier among the first age group to be vaccinated – aged 60 or older – was now being seen for the first time in those aged 55 and older.
Hospitalisations and serious illness are still rising in younger groups who began vaccinations weeks later.
Israel has been conducting a rapid vaccine rollout and its database offers insights into vaccine effectiveness and at what point countries might attain herd immunity.