Medical experts raised questions about data released by Oxford University and AstraZeneca claiming that its coronavirus vaccine is up to 90% effective, The New York Times reports.
The university and the pharmaceutical giant announced this week that its clinical trial found that its vaccine is 62% effective when participants received two full doses but up to 90% effective when participants receive a half-dose followed by a full dose.
The data showed that fewer than 2,800 participants received a half dose compared to 8,900 participants in the full dose trial.
The company did not immediately reveal that it discovered the higher efficacy by “mistake” after some participants were accidentally only given a half-dose.
Though the results are promising because the vaccine, unlike those from Pfizer and Moderna, is cheap and easy to manufacture and store. But scientists now doubt whether the data will stand up under further testing.
“The upshot, the experts said, is that the odds of regulators in the United States and elsewhere quickly authorizing the emergency use of the AstraZeneca vaccine are declining, an unexpected setback in the global campaign to corral the devastating pandemic,” The Times reported.
A spokesperson for AstraZeneca insisted that the trials “were conducted to the highest standards.”
The company said the mistake was made by a contractor but British regulators approved a secondary trial with different doses.
“I think the best way of reflecting the results is in a peer-reviewed scientific journal, not in a newspaper,” executive Menelas Pangalos told the Times.
Along with the mistake, the company did not say how many of the 131 symptomatic cases in their trial were in each group of participants.
The company also pooled together results from its trials in the UK and Brazil even though they were differently designed.
Some have also questioned whether anyone over 55 was involved in the half-dose group.
“I just can’t figure out where all the information is coming from and how it’s combining together,” said Natalie Dean, a biostatistician and an expert in vaccine trial design at the University of Florida, adding that the company and Oxford “get a poor grade for transparency and rigor when it comes to the vaccine trial results they have reported.”
The questions prompted the company’s stock to drop and some are now urging the company to start a new trial.
“The only way they’re going to find out is by specifically and deliberately testing this serendipitous observation,” said John Moore, a professor of microbiology and immunology at Weill Cornell Medical College. “The onus is on them to prove the speculation.”
Pangalos defended the existing data.
“The reality is, it could end up being quite a useful mistake,” he told The Times. “It wasn’t putting anyone in danger. It was a dosing error. Everyone was moving very fast. We corrected the mistake and continued on with the study, with no changes to the study, and agreed with the regulator to include those patients in the analysis of the study as well.”
“What is there to disclose?” he added. “It actually doesn’t matter whether it was done on purpose or not.”