In Israel, vaccination reduced transmission of SARS-CoV-2 to household contacts

In a new study based in Israel, vaccination reduced both the rate of infection with SARS-CoV-2 and household transmission. Evaluating the effectiveness of anti-COVID19 vaccines is essential for pandemic planning. Many studies have already estimated the impact of the vaccines on disease severity and susceptibility. However, estimates of vaccines’ impact on transmissibility are more limited. Israel exclusively adopted the Pfizer-BioNTech mRNA vaccine. To examine this vaccine’s effectiveness against transmission, Ottavia Prunas et al. used statistical approaches that account for data complexities on a healthcare dataset documenting changes in SARS-CoV-2 transmission in Israeli households from June 2020 to July 2021, as the Delta variant emerged. The authors found that vaccinated, subsequently infected people were less infectious than unvaccinated persons. Moreover, less transmission occurred within households with vaccinated members than in those with unvaccinated individuals. However, the ability of the vaccine to prevent transmission waned with time and the advent of the Delta variant. “It is highly unlikely that population-level transmission of SARS-CoV-2 can be eliminated through vaccination alone,” say the authors.