A new joint study by Harvard University and the Clalit Institute for Research examined the effectiveness of Pfizer's third vaccine against the corona virus, and in particular the Delta variant.
The study was published tonight (Saturday) in the leading medical journal The Lancet and is the most comprehensive and thorough study done so far regarding the effectiveness of the booster dose.
Vaccines third dose in Tel Aviv, Photo: Paz Bar
The findings showed that the third vaccine dose reduced coronary heart disease-related hospitalizations by 93%, reduced coronary heart disease by 92%, and reduced coronary morbidity by 81%.
The study included another analysis, which found that in each age group, infection rates began to decline 7-10 days after this age group became eligible for the booster dose.
The correlation between the results of this analysis and the results of the main analysis, performed by different methods and at a different resolution (individual patient level versus population level) increases the certainty that the study findings are accurate.
The researchers used advanced methods to analyze anonymous data from 728,321 Clalit patients who received a third dose of vaccine compared to a control group that included 728,321 patients who received only two doses, about five months or more before.
The data from the vaccinators are in the period ranging from July 30, 2021 to September 23, 2021, in parallel with the fourth wave of the corona in Israel, during which the Delta variant was the dominant strain in the country.
Pfizer vaccines // Photo: AFP,
The matching between the study groups was performed based on an extensive set of demographic, geographic, and health characteristics related to risk for serious illness, health status, and health behaviors.
Allocation to the study groups was performed dynamically based on the daily vaccination status and approximately 198,476 individuals switched from the unvaccinated group to the vaccinated group during the study period.
The size of the study allowed for an accurate assessment of vaccine efficacy over different time periods, different subpopulations (by sex, age and number of comorbidities) and different serious outcomes (which are rarer and therefore require a larger sample).
Also, a recent clinical trial by Pfizer and BioNTech included a smaller sample (10,000 infected) and evaluated the effect of the vaccine on infection and symptomatic disease, but not on more severe outcomes.
Prof. Ben Rice: "The study provides reliable information about the vaccine"
Prof. Ran Blitzer, head of Clalit's innovation division and director of the Clalit Research Institute, said: "These results, published tonight in the scientific journal Lennet, convincingly demonstrate that the third dose of the vaccine is most effective in preventing severe coronary heart disease and hospitalization, "In the population, a week after receiving the booster dose. These results are extremely important and give well-founded and valid information to anyone who is still hesitant about receiving the third dose in Israel and in other countries around the world."
Prof. Ben Rice, director of the Predictive Medicine Group at Boston Pediatric Hospital and Harvard Medical School, said: “One of the main reasons for the hesitation in deciding whether to get vaccinated with the third vaccine dose was a lack of information about vaccine efficacy.
"This rigorous epidemiological study provides reliable information on the effectiveness of the third-dose vaccine, which we hope will help those who have not yet decided to get vaccinated with the booster dose."
In many countries a re-emergence of the corona mite is now being observed despite widespread vaccination.
Possible reasons for this are the higher infection rates in the Delta variant and the reduced immunity of vaccines given months earlier.
In light of this awakening, a number of countries are planning to give a third booster dose of the vaccine.