A health worker presents a bottle of AstraZeneca-Oxford Covid-19 coronavirus vaccine at Patan Hospital near Kathmandu on January 27, 2021.
PRAKASH MATHEMA | AFP | Getty Images
Britain’s decision to postpone the second shot of the AstraZeneca coronavirus vaccine-Oxford University has proven to be an effective strategy, according to the results of a new study.
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 the rate of efficacy increased by a longer interval before the first and second dose. second dose.
“The effectiveness of the vaccine after a single standard dose of vaccine from day 22 to day 90 after vaccination was 76% … and the modeled analysis indicated that protection did not decrease during this initial 3-month period,” the study said. examination at The Lancet medical journal and published Tuesday as a 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 the vaccine is more effective with a longer interval between the first and second dose and that a single dose of vaccine is extremely effective in the first 90 days, providing additional support for current policy.” it is said in the report.
The UK’s current strategy is to vaccinate as many people as possible with a single dose first and to 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 vaccines while they are in limited quantities.
The decision to delay giving people a second booster dose has sparked controversy, and some have questioned whether it could reduce the vaccine’s effectiveness in preventing serious Covid-19 infection.
However, the United Kingdom Joint Committee on Vaccination and Immunization supported this approach. The UK is also delaying the second dose of Pfizer-BioNTech vaccine, a move against which vaccine manufacturers have warned, arguing that there is no data to support a delay.
The study also provided important data on whether the vaccine reduces the transmission of the virus, a previous unknown and a crucial question for policy makers who want to lift the blocking measures that have damaged the economy.
Based on weekly swabs from study volunteers in the UK, a 67% reduction in transmission was found after the first dose of vaccine.
Effective strategy
The latter study supports the British government’s decision, concluding that vaccination programs “intended to vaccinate a large proportion of the population with a single dose, with a second dose administered after a period of 3 months, is an effective strategy for reducing the disease and may be optimal for launching a pandemic vaccine when stocks are limited in the short term. “
The study used additional data from ongoing clinical trials of the vaccine. A separate announcement from AstraZeneca on Wednesday said the vaccine also prevented serious Covid-19 disease, with no severe cases and no hospitalizations more than 22 days after the first dose.
The vaccine was approved by the UK Medicines Authority on December 30 and, as a blow to the UK, is the bulk of the national immunization program, which has been hailed as a success to date.
The UK is about to have vaccinated its first four priority groups (over 70s, residents and staff in nursing homes, health and social care workers and clinically vulnerable clinically) numbering about 15 million people by mid-February.
As of February 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, chief investigator of the Oxford vaccine study and co-author of the study, said that “this new data provides an important verification of the interim data that has been used by more than 25 regulators, including the MHRA and EMA for the vaccine. emergency use authorization. “
“It also supports the policy recommendation made by the Joint Committee on Vaccination and Immunization for a 12-week prime-boost interval, as it seeks the optimal approach to launch and ensures that people are protected after 22 days after a single dose of vaccine. “
The researchers also hope to report data on new variants of the coronavirus in the coming days and expect the results to be largely 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 the age of 65, saying there are not enough test data for this age group. However, the vaccine manufacturer and the British government have defended the jab and say the available data show that it is safe and effective, and more tests will be available soon.