Single dose of AstraZeneca vaccine 76% effective for 3 months
Wednesday, 03 February 2021
The Oxford-AstraZeneca COVID-19 vaccine proved effective at reducing transmission and has a 76% efficacy against symptomatic infection for three months after a single dose, according to a study by the University of Oxford. The study also showed that this efficacy rate against the new coronavirus (Covid-19) increased up to 82% after the second shot, of which administering is delayed, has been given. If the second dose was given under six weeks after the first jab, the efficacy rate was 54.9%.
Participants of the study were swabbed every week to test for evidence of the virus, and the numbers of those testing positive decreased up to half once they had been given two doses of the vaccine. This study, however, did not address concerns around the vaccine about the lack of data on its effectiveness among older people. The Belgian government announced on Tuesday it would not be using the AstraZeneca vaccine for over 55-year-olds.
These findings, published ahead of peer-review, support the strategy behind the UK government’s vaccine rollout policy, which lengthened the interval between both doses to 12 weeks, in effect vaccinating as many people as possible to tackle the coronavirus pandemic. When announced, this strategy provoked controversy, as some questioned whether the efficacy of the vaccine would be lowered.
Andrew Pollard, Chief Investigator of the Oxford Vaccine Trial, said the data showed the 12-week interval between doses was “the optimal approach to roll out, and reassures us that people are protected from 22 days after a single dose”.
Celebrating the study’s findings, UK’s Health Secretary Matt Hancock told BBC radio: “It does show the world that the Oxford jab works, it works well.”