A healthcare professional shows a vial of AstraZeneca-Oxford’s Covid-19 coronavirus vaccine at Patan Hospital, near Kathmandu, on January 27, 2021.
PRAKASH MATHEMA | AFP | Getty Images
The UK’s decision to postpone the second injection of the AstraZeneca-University of Oxford coronavirus vaccine was considered 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 efficacy rate increased with a longer interval before the first and second doses.
“The vaccine’s effectiveness after a single standard dose of vaccine from day 22 to day 90 post-vaccination was 76% … and the modeled analysis indicated that protection did not decrease during this initial 3-month period,” the study, under review in The Lancet medical journal and published on Tuesday as a prepress, found.
The efficacy rate increased to 82.4% when there was an interval of at least 12 weeks 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 the greatest effectiveness of the vaccine is achieved with a longer interval between the first and the second dose, and that a single dose of the vaccine is highly effective in the first 90 days, providing more support for current policy,” said the report.
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 provides at least some partial protection and allows more people to have access to vaccines while they are in limited supply.
The decision to postpone the administration of a second booster dose has sparked controversy and some have questioned whether this could decrease the vaccine’s effectiveness in preventing serious Covid-19 infections.
However, the UK’s Joint Vaccination and Immunization Committee supported the approach. The UK is also delaying the second dose of the 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 transmission of the virus, a previously unknown question and a crucial issue for lawmakers seeking to lift blocking measures that have paralyzed the economy.
Based on weekly swabs from volunteers in the UK study, he found a 67% reduction in transmission after the first dose of the vaccine.
Effective strategy
This latest study supports the UK government’s decision, concluding that vaccination programs “designed 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 to reduce the disease, and may be ideal for launching a pandemic vaccine when supplies are limited in the short term. “
The study used additional data on ongoing clinical trials of the vaccine. A separate AstraZeneca ad on Wednesday showed that the vaccine also prevented serious illnesses caused by Covid-19, with no serious cases and no hospitalizations more than 22 days after the first dose.
The vaccine was approved by the UK drug regulator on December 30 and, like an injection produced in Britain, forms the bulk of the country’s immunization program, which has been hailed as a success so far.
The UK is on track to vaccinate its four priority groups (over 70, residents and staff in nursing homes, first-rate social and health workers and the clinically extremely vulnerable), totaling about 15 million people in the middle of February.
On February 1, more than 9.6 million people received the first dose of the vaccine and just under 500,000 received two doses, according to government data.
Professor Andrew Pollard, principal investigator for the Oxford vaccine trial and co-author of the study, said that “this new data provides important verification of the interim data that has been used by more than 25 regulators, including the MHRA and EMA to grant vaccine emergency use authorization. “
“It also supports the policy recommendation made by the Joint Vaccination and Immunization Committee for a 12-week prime-boost interval, while looking for the ideal approach to implant, and assures us that people are protected 22 days after a single dose of the vaccine . “
The researchers also hope to report data on the new variants of the coronavirus in the coming days, and hope that the findings will be very similar to those already reported by other vaccine developers: that current vaccines work against mutations in the virus.
Germany, France and Sweden are not recommending the AstraZeneca vaccine for people over 65, saying that there is not enough trial data in this age group. The vaccine manufacturer and the UK government have defended the vaccine, however, and say the available data shows that it is safe and effective, with more analyzes set to be made available soon.