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Beating the Odds of Testing Positive: COVID Booster

Ashley L. Faulx, MD, FASGE reviewing reviewing Patalon T, et al. JAMA Int Med 2021 Nov 30.

There are concerns over waning immunity from COVID-19 in terms of antibody dynamics and protection against infection. This study from Israel aimed to determine whether an additional dose of the Pfizer-BioNTech vaccine as a booster would give a short-term protective effect, compared with just the 2-dose regimen. 

Utilizing a national, centralized database, researchers collected data for 306,710 patients and focused analysis on the data from August to October 2021. During this period, more than 500,000 polymerase chain reaction tests were performed, of which 227,380 were for patients who received 2 vaccine doses and 272,852 who received 3 doses. Of the tests, results were positive in 6.6% of the 2-dose group and 1.8% of the 3-dose group. The estimated odds ratio was 0.14 for patients 28 to 65 days after receipt of the booster, translating to an 86% reduction in the odds of testing positive for COVID-19.


This case-controlled analysis shows a clear association between booster vaccination and a significant reduction in the risk of testing positive for COVID, potentially counteracting the waning immunity, at least in these short-term results. Overall rates of infection in the vaccinated population were low, which is reassuring, but these data support the recommendations for a booster shot for our patients.

Ashley L. Faulx, MD, FASGE

Bio and Disclosures


Patalon T, Gazit S, Pitzer VE, Prunas O, Warren JL, Weinberger DM. Odds of testing positive for SARS-CoV-2 following receipt of 3 vs 2 doses of the BNT162b2 mRNA vaccine. JAMA Intern Med 2021 Nov 30. (Epub ahead of print) (