Pfizer COVID vaccine 90% effective vs hospitalization, study finds


The two-dose Pfizer/BioNTech COVID-19 vaccine is 90% effective against hospitalization caused by all SARS-CoV-2 variants, including Delta, for at least 6 months, a Kaiser Permanente and Pfizer study confirmed yesterday in The Lancet.

The researchers retrospectively mined 3.4 million electronic health records of patients 12 years and older from Kaiser Permanente Southern California from Dec 4, 2020, to Aug 8, 2021. Roughly 1.1 million patients had received at least one dose of the Pfizer COVID-19 vaccine, 91% of whom were fully vaccinated, and 6.6% of whom were partially vaccinated.

Among vaccinated cohort members, an average of 3.4 months had elapsed since their second Pfizer dose.

Effectiveness against infection waned

During the study period, 5.4% of patients were infected by SARS-CoV-2. Relative to uninfected patients, a higher proportion of infected patients were younger (median age, 42 vs 45 years), Hispanic (57.7% vs 39.5%), and obese (body mass index of 30 kg/m2 or higher). Among the 6.6% of infections that resulted in hospitalizations, patients were more likely to be older, male, and have more underlying illnesses and greater healthcare use.



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