The head of British drug manufacturer AstraZeneca said on Thursday said that further research was needed on its COVID-19 vaccine after questions emerged over the protection it could offer.
“Now that we’ve found what looks like a better efficacy we have to validate this, so we need to do an additional study,” chief executive Pascal Soriot told Bloomberg in an interview.
He said it would likely 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.”
AstraZeneca and Oxford University on Wednesday acknowledged a manufacturing error that raised questions about preliminary results of their experimental COVID-19 vaccine.
A statement describing the error came days after the company and the university described the shots as “highly effective” and made no mention of why some study participants didn’t receive as much vaccine in the first of two shots as expected.
In a surprise, the group of volunteers that got a lower dose seemed to be much better protected than the volunteers who got two full doses. In the low-dose group, AstraZeneca said, the vaccine appeared to be 90% effective. In the group that got two full doses, the vaccine appeared to be 62% effective. Combined, the drugmakers said the vaccine appeared to be 70% effective. But the way in which the results were arrived at and reported by the companies has led to pointed questions from experts.
The partial results announced Monday are from large ongoing studies in the UK and Brazil designed to determine the optimal dose of the vaccine, as well as examine safety and effectiveness. Multiple combinations and doses were tried in the volunteers. They were compared to others who were given a meningitis vaccine or a saline shot.
Before they begin their research, scientists spell out all the steps they are taking, and how they will analyze the results. Any deviation from that protocol can put the results in question.
But in a statement Wednesday, Oxford University said some of the vials used in the trial didn’t have the right concentration of vaccine so some volunteers got a half dose. The university said that it discussed the problem with regulators, and agreed to complete the late-stage trial with two groups. The manufacturing problem has been corrected, according to the statement.
Experts say the relatively small number of people in the low-dose group makes it difficult to know if the effectiveness seen in the group is real or a statistical quirk. Some 2,741 people received a half dose of the vaccine followed by a full dose, AstraZeneca said. A total of 8,895 people received two full doses.
Additionally, none of the people in the low-dose group were over 55 years old. Younger people tend to mount a stronger immune response than older people, so it could be that the youth of the participants in the low-dose group is why it looked more effective, not the size of the dose.
Another point of confusion comes from a decision to pool results from two groups of participants who received different dosing levels to reach an average 70% effectiveness, said David Salisbury, an associate fellow of the global health program at the Chatham House think tank.
At this stage, Oxford researchers say they aren’t certain why a smaller dose would be more effective and they are working to uncover the reason.
Days before the initial announcement on the results of the trials, Prime Minister Benjamin Netanyahu announced that Israel was close to signing a deal with AstraZeneca to purchase “millions” of doses of its vaccine.
If signed, it would be the third deal signed by Israel to receive vaccinations, following similar deals with Pfizer and Moderna. Israel has also been in talks with Russia to receive its Sputnik V vaccine, though some experts have questioned its opaque certification process.
However, none of the deals guarantees a deadline for the arrival of the vaccines, and with mass global demand, it is still not clear how many doses Israel will get, and when.
Israel has also been working on a homegrown vaccine, though it is currently only in phase 1 trials and its development is expected to take months longer than the foreign candidates. Channel 12 reported Friday that it will likely be available to the public this summer.