New data from Addenbrooke’s Hospital in Cambridge suggests that a single dose of the Pfizer BioNTech vaccine can reduce by four-fold the number of asymptomatic SARS-CoV-2 infections.
This implies that the vaccine could significantly reduce the risk of transmission of the virus from people who are asymptomatic, as well as protecting others from getting ill.
The study by a team at Cambridge University Hospitals NHS Foundation Trust (CUH) and the University of Cambridge analyzed results from thousands of COVID-19 tests carried out each week as part of its screening programs on hospital staff who showed no signs of infection.
Vaccination for health care workers on the CUH site began on 8 December 2020, with mass vaccination from 8 January 2021. During a two-week period between 18 and 31 January 2021, the team screened similar numbers of vaccinated and unvaccinated staff using around 4,400 PCR tests per week.
The results were then separated out to identify unvaccinated staff, and staff who had been vaccinated more than 12 days prior to testing (when protection against symptomatic infection is thought to occur).
The study, which is yet to be peer-reviewed, found that 26 out of 3,252 (0·80%) tests from unvaccinated healthcare workers were positive…