A health worker shows a bottle of AstraZeneca-Oxford 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 shot of the AstraZeneca-Oxford University coronavirus vaccine is an effective strategy.
Researchers at Oxford University found that the Covid-19 vaccine was 76% effective in preventing symptomatic infection for three months after a single dose, and in fact the efficacy rate increased with a longer interval. long before the first and second dose.
“The efficacy of the vaccine after a single standard dose of vaccine from day 22 to day 90 after vaccination was 76% … and modeled analysis indicated that protection did not decrease during this period. initial 3 months, ”the study in The Lancet Medical published Tuesday as a prepress, 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 administered less than six weeks after the first, the efficacy rate was 54.9%.
“These analyzes show that greater vaccine efficacy is obtained with a longer interval between the first and second dose, and that a single dose of vaccine is highly effective in the first 90 days, which provides additional support. for current policy, ”the report states.
The UK’s current strategy is to vaccinate as many people as possible with a single dose and delay the second dose by up to 12 weeks; the idea is that a first dose provides at least some partial protection and allows more people to access the vaccines while they have a limited supply.
The decision to delay the booster dose in people has sparked controversy and some questioned whether it could reduce the effectiveness of the vaccine to prevent a serious Covid-19 infection.
However, the UK Joint Committee on Vaccination and Immunization supported this approach. The UK is also delaying the second dose of the Pfizer-BioNTech vaccine, an action against which vaccine manufacturers have warned, arguing that there is no data to support the delay.
The study also provided important data on whether the vaccine reduces the transmission of the virus, a previous unknown and a crucial issue for policymakers who want to lift the blockade measures that have paralyzed the economy.
Based on weekly swabs from UK study volunteers, a 67% reduction in transmission was found after the first dose of the vaccine.
Effective strategy
The latter study supports the decision of the UK government, which concludes that vaccination programs “aimed at vaccinating a large proportion of the population with a single dose, with a second dose after a period of 3 months, are a strategy effective in reducing the disease and may be optimal for launching a pandemic vaccine when supply is limited in the short term. “
The study used more data from ongoing clinical trials on the vaccine. A separate announcement from AstraZeneca showed Wednesday that the vaccine also prevented serious Covid-19 disease, with no serious cases or hospitalizations more than 22 days after the first dose.
The vaccine was approved by the UK drug regulator on December 30 and, as a feature produced in Britain, makes up the bulk of the country’s vaccination program, which has so far been considered a success.
The UK is on track to have vaccinated its four main priority groups (over-70s, residents and nursing home staff, frontline health workers and social and clinically extremely vulnerable), which have about 15 million people in mid-February.
As of Feb. 1, more than 9.6 million people had received a first dose of vaccine and just under 500,000 had received two doses, according to government data.
Professor Andrew Pollard, lead researcher on the Oxford vaccine trial and co-author of the study, said that “this new data provides an important verification of the provisional data that was used by more than 25 regulators, including the MHRA and the EMA, to grant the vaccine emergency use authorization. “
“It also supports the policy recommendation made by the Joint Vaccination and Immunization Committee for a 12-week first-run interval, as it seeks the optimal approach to deploy it and ensures that people are protected for 22 days. after a dose of the vaccine. “
The researchers also hope to report data on new coronavirus variants in the coming days and hope the findings are broadly similar to those already reported by fellow vaccine development partners: that current vaccines work against virus mutations.
Currently, Germany, France and Sweden do not recommend the AstraZeneca vaccine to people over 65, saying there are not enough test data on this age group. However, the vaccine manufacturer and the UK government have defended the puncture and say the available data show that it is safe and effective, and that more analyzes will be available soon.