Pfizer-BioNTech's COVID-19 vaccine remains effective at preventing hospitalizations for at least six months, a new study suggests..
Researchers at Kaiser Permanente Southern California (KPSC) gathered data from the company's health care network to discover how often fully vaccinated people were either testing positive for the virus or being hospitalized because of it.
They found the Pfizer vaccine was 90 percent effective at preventing hospitalizations for the first six months after becoming fully vaccinated.
Existing variants also seem to have little ability to bypass the vaccines, including the highly transmissible Delta variant, which is now responsible for nearly all cases in the U.S.
The vaccine's effectiveness at preventing infection does significantly wane over time, though, falling as low as 47 percent after five months.
Previous studies have had similar findings regarding the effectiveness of the Covid vaccines at preventing infection and hospitalization.
The Pfizer vaccine's effectiveness at preventing hospitalizations remained steady around 90% among all age groups for six months following the shots
The vaccine's effectiveness at preventing infection waned over time, falling below 50%, though there was no difference among age cohorts
The results of the study show that a recent uptick in breakthrough cases may have less to do with any factors specific to the Delta variant, but instead have to do with the efficacy of the vaccines falling over time.
These breakthrough cases are less serious, though, with the vaccine still showing the ability to prevent hospitalizations and death.
'Our variant-specific analysis clearly shows that the [Pfizer] vaccine is effective against all current variants of concern, including Delta,' said Dr Luis Jodar, senior vice president of Pfizer Vaccines, in a statement.
'COVID-19 infections in people who have received two vaccine doses are most likely due to waning and not caused by Delta or other