A study conducted on more than 300,000 Israelis over 40 years of age confirms the positive impact of the recall dose.
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The protective effect of the third dose of vaccine – or recall dose – against CIVID-19 is now the subject of a broad consensus in the competent scientific community and within the health authorities. American-Israeli works published on Tuesday, November 30 in JAMA Internal Medicine propose an estimated estimate of the expected protection of the “booster” to prevent coronavirus infection, confirming the preceding conclusions of work: the persons who received a third dose From the Pfizer / Biontech RNA vaccine would have a risk decreased by more than 85% of being positive at SARS-COV-2, compared to those who received only the first two injections.
The authors conducted a study on more than 300,000 Israelis over 40 years of age and compared the likelihood of being positive to an RT-PCR test based on the vaccinal status – two or three doses received. The researchers estimated the evolution of this probability as a function of time elapsed since the third stitch.
Consistent numbers
In the first week following the reminder, the effect is weak and the authors warn against possible bias blurring the result. Between seven and thirteen days after the reminder, the probability of presenting a positive test of 60%, and dropped by more than 85% from the end of the second week. As with any observational study, the results should be considered with caution, the authors who do not exclude changes in behavior of individuals after the third dose (less test, for example).
However, these figures are consistent with those published at the end of October in The Lancet by another Israeli team: less than 90% of the hospital admissions one week after the third dose and about 80% reduction in the risk of mortality. Important detail: The analyzes concern the period between early August 2021 and early October 2021, during which the Variant Delta was largely dominant in Israel. These results are therefore not worth the Omicron variant that threatens to supplant the delta in the coming months.