One dose of the Oxford-AstraZeneca or Pfizer-BioNTech vaccine decreases coronavirus infections by 65 per cent. The researchers analysed COVID-19 test results from more than 350,000 people in the UK between December and April. The study shows the impact of vaccination on antibody responses and new infections in a large group of adults from the general population aged 16 years and older. The research was conducted by Oxford University and the Office for National Statistics.
Therevealed that after 21 days of administering single dose of either Oxford-AstraZeneca or Pfizer-BioNTech vaccines, the rates of all new COVID-19 infections had dropped by 65 per cent, symptomatic infections by 72 per cent and infections without reported symptoms by 57 per cent. The protection after taking the second dose of vaccine caused symptomatic infections to fall by 90 per cent and asymptomatic infections by 70 per cent. Vaccines were effective against variants compatible with the Kent strain (B.1.1.7).
The benefits from vaccines in reducing new infections were similar in older individuals over 75 years and under 75 years. The vaccine also helps in the recovery of those reporting long-term health conditions. Dr Koen Pouwels, senior researcher in Oxford University’s Nuffield Department of Population Health, said that 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 reduce hospitalisations and deaths.
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. The antibody responses to a single dose of either vaccine were lower in older individuals who had not had COVID-19 before especially over 60 years. Antibody responses to two Pfizer-BioNTech doses were high across all ages, particularly increasing responses in older people. 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 said,
“Without large community surveys such as ours, it is impossible to estimate the impact of vaccination on infections without symptoms – these have the potential to keep the epidemic going, particularly if people who have been vaccinated mistakenly think they cannot catch COVID-19. “