Reference:
Eyre, D. W., Taylor, D., Purver, M., Chapman, D., Fowler, T., Pouwels, K. B., Walker, A. S., & Peto, T. E. A. (2022). Effect of COVID-19 vaccination on transmission of alpha
and delta variants. New England Journal of Medicine, 386(8), 744-756. https://doi.org/10.1056/NEJMoa2116597
Summary:
This study investigates the effect of COVID-19 vaccinations on the transmission of the alpha (B.1.1.7) and delta (B.1.617.2) variants of SARS-CoV-2. Using contact-tracing data from England, the research finds that while vaccinations significantly reduced transmission of the alpha variant, their effectiveness against the delta variant was diminished. Specifically, vaccinated individuals exhibited similar viral loads as unvaccinated individuals when infected by the delta variant, suggesting a reduced ability of vaccination to prevent its spread. The study also noted a decline in transmission protection over time post-vaccination. Overall, the findings imply that while vaccination remains crucial, its role in controlling delta variant transmission is limited compared to the alpha variant.