Protection against symptomatic COVID-19 begins to decrease about one month from initial vaccination, while immunity against severe COVID-19 remains high for about six months, according to a recent study by scientists at Penn State College of Medicine.
In the largest study to date, researchers analyzed data from 7 million unvaccinated and vaccinated individuals aged 12 and older.
The researchers determined the vaccines provided significant protection against COVID-19, but their effectiveness decreased over time.
The findings showed that after full vaccination, immunity against COVID-19 infection decreased from 84% after the first month to 22% after five or more months.
Those who received the Moderna vaccine had the highest levels of protection, according to the findings.
Researchers said vaccines remained 90% effective against severe COVID-19 for up to six months. But protection against severe COVID-19 was lower for individuals who received the Johnson & Johnson vaccine.
The study also found immunity against COVID-19 decreased more rapidly for people 65 or older, no matter which vaccine they received.
The researchers didn’t have data beyond six months, and the study didn’t include data on boosters.