Photographer: Dhiraj Singh / Bloomberg
Photographer: Dhiraj Singh / Bloomberg
AstraZeneca Plc’s Covid vaccine showed an 82% effectiveness three months apart between two injections, according to a new study supporting the UK’s controversial decision to adopt an extended dosing interval.
The vaccine can also significantly reduce the transmission of the virus, according to analysis of research data by the University of Oxford, who co-developed the shot with the British drug company. Swabs taken from volunteers in the UK arm of the study showed a 67% reduction in transmission after the first dose, the report showed.
The UK has agreed to give the first and second injections of vaccines with two injections four to 12 weeks apart in an attempt to stretch scarce supplies while ramping up production. AstraZeneca executives had previously said that the longer gap, compared to the three to four week interval between injections recommended for other vaccines, could also increase effectiveness.
Covid-19 vaccinations exceed 100 million doses worldwide
The new results are a further boost to the immunization program in the UK, which has jumped ahead of the countries of the European Union and has given 14% of residents a first injection. If the Astra vaccine also reduces transmission, it speeds up the process of achieving herd immunity when the virus can no longer enter a population.
According to new data, vaccine efficacy increased from 55% at a dosing interval of less than six weeks to 82% at an interval of 12 weeks or more. The analysis also showed that the shot showed 76% protection after the first of two injections. That level of immunity was reached from 22 days after the first shot.
The AstraZeneca vaccine had shown an average of 70% protection in previous results of broad clinical studies. Those results came from two subgroups, one of which delivered 62% efficacy, the other 90%, with different dose levels in the two groups. When the UK approved the vaccine in December, regulators said they thought the discrepancy was more likely related to the interval between injections than the dose level.
More cases
Initial results were based on 131 cases of symptomatic Covid-19 in the studies, a number that has since grown to 332, allowing for a more in-depth analysis. The new data is based on information from more than 17,000 trial participants in the UK, Brazil and South Africa, Oxford said.
The European Union has also approved the vaccine, with France, Germany and some other countries limit its use in the elderly, citing a lack of research data in older age groups.
“These new data are an important verification of the interim data used by more than 25 regulators,” Andrew Pollard, lead investigator of the Oxford study and co-author of the paper, said in a statement. It also supports the policy recommendation of the UK vaccine advisory panel, he said.
Oxford also plans to publish data on the vaccine’s interaction with new ones variants of the coronavirus in the coming days. The university 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 coronavirus variants, but it plans to initiate human studies on a booster shot for a South African strain that could accelerate immunity decline. Pfizer Inc. is also looking for a booster shot.
– Assisted by Stephanie Baker
(Updates with more data from the report from the fourth paragraph)