Addenbrooke's study finds single dose of Pfizer vacccine dramatically reduces asymptomatic Covid infections

  • Hear more about the research from Dr Mike Weekes, who led the study. He spoke to ITV News Anglia's Becky Jago earlier today.


New data from Addenbrooke's Hospital in Cambridge, and Cambridge University, shows a single dose of the Pfizer BioNTech jab not only protects people from getting ill, but also dramatically reduces the chances of them spreading the virus to others.

According to the research, one dose of the vaccine can reduce by four-fold the number of asymptomatic Covid-19 infections.

This suggests that the vaccine could significantly reduce transmission of the virus among people who have no symptoms, as well as protecting others from getting ill.

This is great news, the Pfizer vaccine not only provides protection against becoming ill from SARS-CoV-2 but also helps prevent infection, reducing the potential for the virus to be passed on to others. This will be welcome news as we begin to plot a roadmap out of the lockdown, but we have to remember that the vaccine doesn’t give complete protection for everyone.

Dr Mike Weekes, infectious disease specialist who led the study
Addenbrooke's Hospital worked with Cambridge University to produce the data. Credit: ITV News Anglia

Vaccination for health care workers on the sites of Cambridge University Hospitals NHS Foundation Trust Sites, which Addenbrooke's belongs to, began on the 8th of December 2020, with mass vaccination from the 8th of January 2021.

Throughout the pandemic so far, we have taken a systematic approach to keeping our staff safe and well. The huge efforts of all those involved in the testing, tracing and vaccination programmes at CUH are making the plan a reality. We are very encouraged by the findings of our research. It gives further hope for the near future.

Giles Wright, programme director for the CUH Vaccination Hub
Thousands of Covid-19 tests were analysed to gather the data. Credit: ITV News Anglia

Thousands of Covid-19 tests were analysed to gather the data as part of a screening programme on hospital staff who showed no signs of infection.

The study found that 26 out of 3,252 tests from unvaccinated healthcare workers were positive. This compared to 13 out of 3,535 tests from healthcare workers less than 12 days post-vaccination and 4 out of 1,989 tests from healthcare workers at 12 days or more post-vaccination.

This suggests a four-fold decrease in the risk of asymptomatic Covid infections amongst healthcare workers who have been vaccinated for more than 12 days.

When the team included healthcare workers who did have symptoms, their analyses showed similar reductions.

This is fantastic news for both hospital staff and patients, who can be reassured that the current mass vaccination strategy is protecting against asymptomatic carriage of the virus in addition to symptomatic disease, thereby making hospitals even safer places to be.

Dr Nick Jones, first author on the study and an infectious diseases/microbiology registrar at CUH
The study suggests a four-fold decrease in the risk of asymptomatic Covid infections amongst healthcare workers who have been vaccinated. Credit: ITV News Anglia