Observational study in Qatar showed the effectiveness of Pfizer vaccine against any SARS-CoV-2 infection dropped to 20% in months 5 through 7 after the second dose, but effectiveness against severe Covid-19 remained high.
Cohort study: Pfizer vaccine effectiveness against any infections declined from 88% during the first month after full vaccination to 47% after 5 months. Vaccine effectiveness against hospital admissions remained high; 87% within 1 month, and 88% at 5 months after full vaccination, with no significant waning.
Commentary on Twitter
New on breakthrough infections in 620,000 Veterans
"Vaccine protection declined by mid-August 2021, decreasing from 91.9% in March to 53.9%"https://t.co/xonBb4aEqJ highest reduction with J&J vaccine pic.twitter.com/rbhXOREFPP
— Eric Topol (@EricTopol) October 15, 2021