Results from real-world use of Pfizer and BioNTech’s BNT162b2 show that two doses of the mRNA-based vaccine can cut the number of symptomatic COVID-19 infections by 94%, whilst also reducing severe illness by 92%. The Clalit Research Institute’s preliminary findings come from an analysis of around 1.2 million people in Israel, half of whom received the full two-dose course of BNT162b2.
Ran Balicer, chief innovation officer at Israel’s health maintenance organisation Clalit, said, “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.” Final results from Pfizer and BioNTech’s phase 3 study found that BNT162b2 demonstrated an efficacy rate of 95% in preventing COVID-19 in participants without evidence of prior SARS-CoV-2 infection.
Protection across all age groups
The analysis by the Clalit Research Institute also found that the efficacy of BNT162b2 was maintained in all age groups, including those over 70 years old. Further, researchers suggested that protection is expected to rise as more data accumulate beyond seven days after the second vaccine dose. “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,” Balicer noted.
The Clalit Research Institute is set to publish full results in the coming weeks, including potential findings on the degree to which BNT162b2 blocks transmission of the virus.
Limits of observational study
While the findings from Israel come from an observational study, the researchers tried to account for drawbacks associated with these types of analysis. “The vaccinated group was tested against a control group of about 600,000 non-vaccinated people who were carefully adjusted so 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 Clalit Research Institute explained.
The researchers added “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.” The Clalit Research Institute suggested that such a design “allows to fully normalise the impact of events that happened in parallel – such as the effect of quarantine, and changing vaccine contraindications.”