COVID vaccines protect against Delta but don’t fully stop disease spread


While COVID-19 vaccines lower the likelihood of infection with the highly transmissible SARS-CoV-2 Delta (B1617.2) variant, the virus can still be transmitted within households—but less so than among unvaccinated people—a study today in The Lancet Infectious Diseases finds.

Led by Imperial College London researchers, the study evaluated community COVID-19 transmission and viral loads among 602 vaccinated and unvaccinated contacts of 471 mildly ill coronavirus outpatients ages 5 years and older from Sep 13, 2020, to Sep 15, 2021. For up to 20 days, 133 participants contributed 8,145 upper respiratory tract samples, regardless of whether they had symptoms.

Of 205 household contacts of COVID-19 patients infected with Delta, 62% had received two vaccine doses, 19% had received one dose, and 19% were unvaccinated.



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