J&J Wanes After 6 Months(Study)[2021]
The November study, published in Science, examined COVID-19 infection and deaths by vaccination status of more than 780,000 U.S. Veterans. Researchers from the Public Health Institute, the Veterans Affairs Medical Center, and the University of Texas Health Science Center compared the vaccine's effectiveness in March to that in September.
They found that the Pfizer-BioNTech vaccine’s effectiveness against infection dropped to 43.3% from 86.9% after six months. The Moderna vaccine saw a similar decline, falling to 58.0% from 89.2%. They observed the largest drop in the Johnson & Johnson vaccine, which was 13.1% effective in September compared to 86.4% in March.
https://www.verywellhealth.com/vaccine-covid-effectiveness-5209145
https://www.science.org/doi/10.1126/science.abm0620