COVID-19 vaccines stop protecting after six months

For people who are at risk, timely revaccination against coronavirus is necessary, because after six months, existing vaccines no longer provide the necessary protection, journal Lancet Respiratory Medicine writes.

According to Medportal.ru, the researchers studied data on 50,000 hospitalizations from April through November 2021 and found that the vaccines were 94% effective in preventing hospitalizations 50-100 days after the shot. However, after 200-250 days, efficacy drops to 80.4%. Overall, the study confirms a dramatic decrease in protection as early as six months after vaccination, indicating the need for additional measures, i.e., booster vaccination.

Researchers were also able to identify factors associated with decreased vaccine effectiveness: older age (80+), comorbidities such as cancer, transplants, chronic kidney disease, hypertension or heart failure, type of infection, and time since vaccination.

The study found that Moderna, Pfizer-BioNTech and Janssen vaccines provided about the same initial protection against coronavirus, with Pfizer-BioNTech and Janssen decreasing in effectiveness over time faster than Moderna protection.

The scientists say these data help understand differences in efficacy by vaccine type, which may help guide the goals of booster vaccination programs.