AstraZeneca revises down efficacy rate of US Covid-19 vaccine trial


AstraZeneca has revised the efficacy rate for its US Covid-19 vaccine trial down to 76 per cent as the pharmaceutical group sought to address concerns that it had published incomplete interim data earlier this week. 

Mene Pangalos, AstraZeneca’s executive vice-president, said a reassessment showed the data were “consistent” with the previously reported numbers, which had an efficacy rate of 79 per cent. 

The latest challenge to AstraZeneca followed a bruising few weeks for the company, with the independent US data monitoring board that oversaw its clinical trial objecting to the initial data release as potentially misleading. The Anglo-Swedish pharmaceutical group has also been locked in a bitter battle with the EU over accusations it has failed to meet supply targets.

Anthony Fauci, director of the National Institute for Allergy and Infectious Diseases, said this week that the data and safety monitoring board that oversaw the clinical trial had sent a “rather harsh note” to him and AstraZeneca. 

The monitoring board was concerned that the interim data, with a cut-off date of mid-February, would show a more positive efficacy rate, writing that it thought the actual rate could be between 69 and 74 per cent. 

In response, AstraZeneca accelerated its analysis, which involved examining each additional case to see whether it was really Covid-19. 

This “confirms that our Covid-19 vaccine is highly effective in adults, including those aged 65 years and over”, Pangalos said. The jab, developed with Oxford university, was also found to be 85 per cent effective in older adults, higher than the previously reported figure of 80 per cent and prevented all severe disease and hospitalisation. 

“We look forward to filing our regulatory submission for emergency use authorisation in the US and preparing for the rollout of millions of doses across America,” Pangalos said. 

The US trial included more than 32,000 participants, two-thirds of whom took the vaccine with one-third on a placebo. It resulted in 190 cases of symptomatic Covid-19, according to the new analysis, 49 more than were tallied in the initial analysis. There were 14 more cases left to be confirmed as Covid-19, meaning the efficacy rate could shift slightly. 

The fuller data still revealed a higher efficacy rate than in the trial conducted outside the US, which was used to win regulatory approval in the UK and the EU. That trial resulted in an average efficacy rate of 70 per cent at preventing symptomatic Covid-19.

The data will be submitted for peer-reviewed publication in the coming weeks.

AstraZeneca is also mired in a conflict with the EU over alleged supply shortfalls and concerns about side-effects. The company’s low-cost jab was intended to be an essential part of the bloc’s vaccination efforts.

Italy said on Wednesday it had discovered a stockpile of 29m AstraZeneca vaccine doses in a facility in the country. The company said it was “incorrect” to describe the vaccines that way, adding that the doses were awaiting “quality control” processes.

The disclosure prompted further recriminations from Brussels, with Valdis Dombrovskis, EU trade commissioner, saying the drugmaker was “promising to deliver 30m doses but they are not even close to this figure”.

AstraZeneca said it had made its “best efforts” as required by the contract signed with the European Commission last year, and blamed low product yields at a plan in Belgium for the delays.

The company also said this week that the US monitoring board had looked into concerns about rare blood clots associated with the vaccine with the help of an independent neurologist and found no problems. 

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