AstraZeneca COVID Vaccine Set for New Trials After Scientists Raise Doubts Over Initial Data

Drugmaker AstraZeneca is expected to begin further trials of its potential COVID-19 vaccine, after scientists raised doubts about data on its effectiveness.

The British-Swedish company, which developed the vaccine with the University of Oxford in the U.K., became the third company in a week to reveal it may have found a vaccine that was highly effective at preventing symptoms.

However, scientists had raised concerns about the vaccine's levels of effectiveness after it emerged the interim data had been taken from two separate sub-trials—in the U.K. and Brazil—which brought varying degrees of success.

One, in which participants received two full doses a month apart, showed the vaccine was 62 percent effective. The other, in which people were given a half dose followed by a full dose, showed the vaccine was 90 percent effective.

It later emerged that the seemingly more successful method had only been tested after a contractor accidentally administered half doses to volunteers, and that it had not been tested on those older than 55, who are most at risk to COVID-19.

Neither point had been included in AstraZeneca's original news release.

"Now that we've found what looks like a better efficacy we have to validate this, so we need to do an additional study," the company's CEO, Pascal Soriot, said on Thursday, in his first interview since the initial data were released.

It is likely to be another "international study, but this one could be faster because we know the efficacy is high so we need a smaller number of patients," he added.

The new trial is expected to focus on the more successful half-dose, full-dose method.

Soriot said he did was not expect the additional trial to hold up regulatory approvals in the U.K. and European Union, and that authorization in some countries is still expected before the end of the year.

Approval of the vaccine by the U.S. Food and Drug Administration may take longer because the regulator is unlikely to rubber-stamp it on the basis of studies conducted elsewhere, he added.

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An illustration picture shows vials with COVID-19 Vaccine stickers attached and syringes with the logo of British pharmaceutical company AstraZeneca on November 17, 2020. JUSTIN TALLIS/AFP via Getty Images

When combining data from the two dosing regimens, Oxford and AstraZeneca said the vaccine is 70.4 percent effective—although we still need more results to be peer-reviewed before the effectiveness of the jab can be fully assessed.

The U.S.'s Operation Warp Speed, which aims to help COVID vaccine development, was among those to have raised questions about Oxford-AstraZeneca's variable results.

Its head, Moncef Slaoui, revealed on Tuesday that over-55s had not been included in the trial which suggested the highest efficacy.

During a press briefing, he added: "The 90 percent efficacy group and the 62 percent efficacy group are overlapping statistically, so it is still possible that that difference is a random difference. It's unlikely but it's still possible it's a random difference."

Speaking before news of the extra Oxford-AstraZeneca trial was announced, Stephen Evans, professor of pharmacoepidemiology at the London School of Hygiene and Tropical Medicine, said that both sub-trial and single trial methods were legitimate.

However, he added that variations between trials could potentially be problematic. "It is better to have one big trial," he told The Times newspaper.

Last week, U.S. manufacturers Pfizer and Moderna also released data showing that each of their vaccines offered 95 percent protection. That figure came from single Phase 3 clinical trials, each of which involved about 30,000 people.

The graphic below, provided by Statista, shows the effectiveness of the top COVID-19 vaccine candidates.

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How effective are the COVID-19 vaccine candidates? Statista