Research clearly shows that vaccines against the SARS-CoV-2 virus reduce hospital admissions and deaths and also the risk of long Covid. Recent research by the University of Geneva looks at the impact of vaccines on infectiousness.
The research, published on 8 April 2022 in Nature Medicine, looks at the impact of vaccination on the infectious viral load (a proxy for infectiousness) of those vaccinated and subsequently infected with the Delta and Omicron variants compared to people who were unvaccinated.
After two doses of vaccine those subsequently infected with Delta had substantially lower infectious viral loads than unvaccinated patients. However, lower infectious viral loads were only observed after three shots among those subsequently infected with Omicron suggesting that three jabs are required to contain the variant’s spread.
The research also suggests that Omicron might be able to infect with a lower viral load than Delta and that mechanisms other than viral load contribute to the high infectiousness of SARS-CoV-2 Omicron.
Nature medicine article (in English)