In a new study from Kaiser Permanente, researchers found that one month after a third dose, the Pfizer-BioNTech COVID-19 vaccine conferred higher effectiveness against infection and hospitalization than two doses of the vaccine after one month.
The team says when they looked at the effectiveness of the two doses of Pfizer–BioNTech vaccine versus three doses, they saw a benefit with three doses that exceed that achieved with two doses alone.
In the study, the team tested the primary series of two doses of the Pfizer-BioNTech COVID-19 vaccination effectiveness against infection, hospitalization, and death up to eight months after vaccination.
They also assessed the effectiveness of three doses of the vaccine up to three months after vaccination.
To assess effectiveness, this research evaluated the electronic health records of 3.1 million members of Kaiser Permanente.
During the study period, 197,535 (6.3 percent) patients were infected with SARS-CoV-2, and of those, 15,786 (8 percent) were admitted to the hospital.
During the study period, the predominant variant was delta, and not omicron.
The team found two-dose vaccine effectiveness against infection declined from 85 percent during the first month after vaccination to 49 percent up to eight months following vaccination.
Two-dose vaccine effectiveness against hospitalization remained high (90 percent) throughout the eight months and did not wane, except among people who were 75 years of age and older, or who had compromised immune systems.
For people who were immunocompromised, the protection against hospitalization dropped to 74 percent, and for those 75 and older, it was 77 percent.
Three-dose vaccine effectiveness was 88 percent against infection and 97 percent against hospitalization within the first three months after vaccination.
The team says the public health impact of a third dose to prevent severe disease is substantial.
Importantly, all studies that have evaluated the vaccine effectiveness of a third dose—including ours—have shown a meaningful improvement in vaccine effectiveness against a broad range of SARS-CoV-2 outcomes.
If you care about Covid, please read studies that COVID-19 vaccines can effectively cut ICU stay, and new inhaled vaccine delivers broad protection against COVID-19, variants.
For more information about Covid, please see recent studies that people with COVID-19 infections may age much faster, and results showing this pill can release RNA in the stomach, offer a new way to administer vaccines.
The study is published in The Lancet Regional Health-Americas and was conducted by Sara Y. Tartof et al.
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