A health worker displays a vial of AstraZeneca-Oxford’s Covid-19 coronavirus vaccine at Patan Hospital near Kathmandu on January 27, 2021.
PRAKASH MATHEMA | AFP | Getty Images
According to the results of a new study, the UK’s decision to delay the second admission of the AstraZeneca-University of Oxford coronavirus vaccine has proven to be an effective strategy.
Researchers at the University of Oxford found that the Covid-19 vaccine was 76% effective in preventing symptomatic infection for three months after a single dose, and in fact, efficacy increased with a longer interval before the first and second doses.
“The efficacy of the vaccine after a single standard dose of vaccine from day 22 to day 90 post-vaccination was 76% … and modeled analysis indicated that protection did not decrease during this initial 3-month period,” said the study, which reported. reviewed by The Lancet Medical journal and published Tuesday as preprint, found.
The efficacy rate increased to 82.4% when there was at least a 12-week interval before the second dose. When the second dose was given less than six weeks after the first, the efficacy rate was 54.9%.
“These analyzes show that higher vaccine effectiveness is obtained with a longer interval between the first and second dose, and that a single dose of vaccine is very effective in the first 90 days, providing further support for current policies,” the report said. .
The UK’s current strategy is to vaccinate as many people as possible with a single dose first and delay the second dose for up to 12 weeks; the idea is that a first dose will provide at least partial protection and allow more people access to the vaccines while their availability is limited.
The decision to delay humans for a second booster dose has sparked controversy, and some have questioned whether it could reduce the vaccine’s efficacy in preventing severe Covid-19 infection.
The UK Joint Committee on Vaccination and Immunization supported the approach. The UK is also delaying the second dose of the Pfizer-BioNTech vaccine, a step the vaccine manufacturers have warned against, arguing that there is no data to support a delay.
The study also provided important data as to whether the vaccine reduces the transmission of the virus, a previously unknown and crucial question for policymakers looking to lift lockdown measures that have paralyzed the economy.
Based on weekly smears from volunteers in the UK study, a 67% reduction in transmission was found after the first dose of the vaccine.
Effective strategy
This latest study supports the UK government’s decision and concludes that vaccination programs “aimed at vaccinating a large proportion of the population with a single dose, with a second dose given after a 3-month period, is an effective strategy to reduce the risk of disease. disease, and optimal for pandemic vaccine rollout when supplies are limited in the short term. “
The study used further data from ongoing clinical trials of the vaccine. A separate announcement from AstraZeneca on Wednesday showed that the vaccine also prevented severe Covid-19 disease, with no serious cases and no hospitalization more than 22 days after the first dose.
The vaccine was approved by the UK drug regulator on Dec. 30 and, like a shot produced in Britain, constitutes the bulk of the national immunization program, which has thus far been considered a success.
The UK is on track to vaccinate the four main priority groups (over-70s, residents and staff in retirement homes, primary health and social workers and the clinically extremely vulnerable) by mid-February.
By February 1, more than 9.6 million people had received a first dose of the vaccine and just under 500,000 had received two doses, according to government data.
Professor Andrew Pollard, principal investigator of the Oxford vaccine study and co-author of the study, said: “These new data are an important verification of the interim data used by more than 25 regulators, including the MHRA and EMA to develop the vaccine grant authorization for emergency use. “
“ It also supports the policy recommendation of the Joint Vaccination and Vaccination Committee for a 12-week prime-boost interval, as they seek the optimal approach to roll-out, and assures us that people are protected from 22 days after a single dose of the vaccine. “
The researchers also hope to report data on the new coronavirus variants in the coming days, and expect the findings to be broadly similar to those already reported by fellow vaccine developers – that current vaccines work against mutations in the virus.
Germany, France and Sweden do not currently recommend the AstraZeneca vaccine for people over 65, saying there is not enough research data on this age group. However, the vaccine maker and the UK government have defended the shot, saying the available data shows it to be safe and effective, and more analyzes will be available soon.