Photographer: Dhiraj Singh / Bloomberg
Photographer: Dhiraj Singh / Bloomberg
AstraZeneca Plc’s Covid vaccine showed 82% effectiveness with a three-month interval between two vaccines, according to a new study that reinforces the UK’s controversial decision to adopt an extended dosage range.
The vaccine can also significantly reduce the transmission of the virus, according to analysis of trial data from the Oxford University, which developed the shot with the British pharmaceutical. Swabs taken from volunteers in the UK study arm showed a 67% reduction in transmission after the first dose, the report showed.
The UK has approved giving the first and second injections of two-dose vaccines every four to 12 weeks, in an effort to stretch scarce supplies as manufacturing increases. AstraZeneca executives had previously said that the longer interval, compared to the three to four week period between vaccines recommended for other vaccines, could also increase effectiveness.
Covid19 Vaccinations exceed 100 million doses worldwide
The new results are yet another boost to the UK’s immunization program, which ran ahead of European Union countries and gave initial vaccines to 14% of residents. If the Astra vaccine also reduces transmission, it will speed up the process of obtaining herd immunity when the virus can no longer invade the population.
The vaccine’s effectiveness increased from 55% with a dose interval of less than six weeks to 82% when spaced 12 weeks or more, according to new data. The analysis also found that the injection showed 76% protection after the first of the two injections. This level of immunity was reached after 22 days after the first injection.
The AstraZeneca vaccine showed an average protection of 70% in previous results of extensive clinical trials. These results came from two subsets, one of which delivered 62% effectiveness, the other 90%, with different dosage levels in the two groups. When the United Kingdom approved the vaccine in December, regulators signaled that they thought the discrepancy was more likely to be linked to the interval between vaccines than to the dosage level.
More Cases
Initial results were based on 131 symptomatic Covid-19 cases in the trials, a number that has since grown to 332, allowing for further analysis. The new data is based on information from more than 17,000 test participants in the UK, Brazil and South Africa, said Oxford.
The European Union also approved the vaccine, with France, Germany and some other countries restrict its use in the elderly, citing the lack of data from trials in older age groups.
“This new data provides an important verification of the interim data used by more than 25 regulators,” said Andrew Pollard, chief investigator for the Oxford study and co-author of the article, in a statement. It also supports the policy recommendation made by the UK vaccine advisory panel, he said.
Oxford also plans to publish data on how the vaccine interacts with new coronavirus variants in the coming days. The university said it expects the findings to be in line with those of other developers.
Moderna Inc. said last month that its vaccine will protect against two known variants of the coronavirus, but plans to start human studies of a booster injection for a South African strain that could cause immunity to decrease more quickly. Pfizer Inc. is also looking to develop a booster injection.
– With the help of Stephanie Baker
(Updates with more report data starting in the fourth paragraph)