Vaccine Effectiveness:  1.2 Million People Can’t Be Wrong –

Evidence from Israel’s Largest HMO

By Shlomo Maital   

Prof. Ran Balicer, Clalit HMO

    The largest study to date of vaccine effectiveness, in the field, will be shortly published in the New England Journal of Medicine, based on data from Israel’s largest HMO, Clalit – 1.2 million people!  The lead author is Prof. Ran Balicer, who heads innovation at Clalit and is a highly creative doctor.

     Here are the main results,  reported by Times of Israel:   

    A massive study by Israel’s largest health provider indicates that the Pfizer-BioNTech vaccine is 94 percent effective in preventing symptomatic COVID-19, and 92% effective in averting serious cases of the disease.    The survey by the Clalit Health Services HMO compared 600,000 fully vaccinated individuals — 170,000 over 60 and 430,000 between the ages of 16 and 59 — with 600,000 unprotected Israelis. Believed to represent the largest such study in the world to date, it found the vaccine to be highly protective from both symptomatic infections and serious symptoms, shoring up previous studies on the shots.   “The previous studies dealt with infections, but not with symptoms and therefore can’t be compared to Pfizer’s clinical research,” said Dr. Ran Balicer, an epidemiologist who directs health policy planning at Clalit, in an interview with Channel 12. “Now, for the first time, we are comparing the vaccinated group with a control group with similar characteristics to see if the vaccine works ‘by the book.’”   After accounting for factors such as age, “we can state clearly: The vaccine prevents serious illness also among those 70 and older, for whom there wasn’t enough data in Pfizer’s study,” said Balicer, who analyzed the data along with several Israeli researchers and a team from Harvard University.  

  The team, including Harvard University researchers, who did the research used sophisticated statistical techniques, including “twinning” —   matching people similar in age, gender and other characteristics,  one with the vaccine and one without.    

    Israel has four main large HMO’s.  Each has a sophisticated IT database.  This has made it possible to vaccinate very large numbers of Israelis, based on priorities, in an orderly manner and to track the results – and share them with Pfizer, which was a condition for Pfizer supplying large numbers of doses. 

     The existence of medical database records is a key advantage of a health system based on HMO’s and publicly provided healthcare.  Such databases exist in the US, but are fragmented and are zealously protected, ostensibly for ‘privacy’ but also in large part for commercial reasons (the data are highly valuable).