The COVID-19 Infection Survey, a partnership between the University of Oxford, the Office of National Statistics (ONS) and the Department for Health and Social Care (DHSC), has released data that shows the impact of vaccination on antibody responses and new infections in adults aged 16 years and older.

Researchers analysed nose and throat swabs and found that 21 days after a single dose of either Oxford-AstraZeneca or Pfizer-BioNTech vaccines (with no second dose), the rates of all new COVID-19 infections had dropped by 65%, symptomatic infections by 72% and infections without reported symptoms by 57%.

Dr Koen Pouwels, senior researcher in Oxford University’s Nuffield Department of Population Health, says, ‘The protection from new infections gained from a single dose supports the decision to extend the time between first and second doses to 12 weeks to maximise initial vaccination coverage and reduce hospitalisations and deaths.

“However, the fact that we saw smaller reductions in asymptomatic infections than infections with symptoms highlights the potential for vaccinated individuals to get COVID-19 again, and for limited ongoing transmission from vaccinated individuals, even if this is at a lower rate. This emphasises the need for everyone to continue to follow guidelines to reduce transmission risk, for example through social distancing and masks.”

The second study compared how antibody levels changed after a single dose of either Oxford-AstraZeneca or Pfizer-BioNTech vaccines, or two doses of the Pfizer-BioNTech vaccine. In individuals who had not had COVID-19 before, antibody responses to a single dose of either vaccine were lower in older individuals, especially over 60 years. 

David Eyre, Associate Professor at the Big Data Institute at the University of Oxford, says, “In older individuals, two vaccine doses are as effective as prior natural infection at generating antibodies to the SARS-CoV-2 virus that causes COVID-19 – in younger individuals a single dose achieves the same level of response. Our findings highlight the importance of individuals getting the second vaccine dose for increased protection.”

Sarah Walker, Professor of Medical Statistics and Epidemiology at the University of Oxford and Chief Investigator and Academic Lead for the COVID-19 Infection Survey added, “We don’t yet know exactly how much of an antibody response, and for how long, is needed to protect people against getting COVID-19 in the long-term – but over the next year, information from the survey should help us to answer these questions. “

The group will continue to monitor the pandemic on a weekly basis to look for warning signs of infection rates rising within specific regions and groups in order to monitor the immunity against COVID-19.

Health Minister Lord Bethell said, “Studies like the ONS COVID-19 Infection Survey are critical to helping us build a picture of COVID-19 infections across the UK and I thank all those who took part and conducted this vital research.”

Health Secretary Matt Hancock said, “With over 33 million first jabs already in arms, saving lives and cutting the risk of infection, it’s vital everyone gets their second dose when invited, to protect you and your loved ones against this disease. The vaccine programme has shown what our country can achieve when working as one, it is our way out of the pandemic. When you get the call, get the jab.”


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