The first dose of a COVID-19 vaccine was enough to push infections down by 65%, a new study has shown.
The analysis, conducted by the COVID-19 Infection Survey, a partnership between the University of Oxford, the Office of National Statistics and the Department for Health and Social Care, examined people who had received a jab of Oxford-AstraZeneca (LON:AZN) or Pfizer-BioNTech.
Researchers analysed 1.6mln test results from nose and throat swabs taken from 373,402 study participants between 1 December 2020 and 3 April 2021.
Three weeks after a single dose of a jab, the rates of all new COVID-19 infections had dropped by 65%, symptomatic infections by 72% and infections without reported symptoms by 57%.
A second study compared how antibody levels changed after a single dose of either vaccine or two doses of the Pfizer-BioNTech.
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. Antibody responses to two Pfizer-BioNTech doses were high across all ages, particularly increasing responses in older people to reach similar levels to those receiving a single dose after prior infection.
In a separate announcement, the University of Oxford said that the risk to mothers and babies is greater than acknowledged at the beginning of the pandemic, and that health priority measures should include pregnant women.
This is after a study of more than 2,100 pregnant women across 18 countries worldwide has revealed that COVID-19 is associated with the risk of maternal and newborn complications.