Positive but confusing, AstraZeneca’s latest clinical trial results left many experts wishing to see more data before final judgment is passed on how well the vaccine will execute.
A volunteer taking part in the AstraZeneca vaccine trial having blood drawn in Oxford, England, last week, with face mask.
An influx of news about experimental vaccines to prevent Covid-19 has emerged this month, with AstraZeneca and the University of Oxford and their latest development. On Monday a preliminary analysis revealed their vaccine was effective, they reported — particularly when the first dose was cut in half mistakenly.
The announcement came on the heels of stunning reports from Moderna, as well as Pfizer and BioNTech. But AstraZeneca’s news was murkier, leaving many experts wanting to see more data before final judgment is passed on how effective the vaccine may turn out to be.
AstraZeneca vaccine, what is it?
Researchers at the University of Oxford used a kind of virus to develop a vaccine that typically causes colds in chimpanzees, called an adenovirus. They genetically altered the virus so that a gene is carried for a coronavirus protein, which would theoretically train the immune system in a human to recognize the actual coronavirus.
Johnson & Johnson, as well as labs in China, Italy, and elsewhere, also tested the adenovirus-based vaccines. In Russia, an adenovirus-based vaccine called Sputnik V is already being distributed on an emergency basis, although the results from their late-stage trial have yet to be published in detail.
Adenovirus-based vaccines have been being tested by researchers for decades, but it wasn’t until July of this year that the first one was licensed as Johnson & Johnson got approval from European regulators for an Ebola vaccine.
What has been found by the AstraZeneca trials?
AstraZeneca and Oxford began doing clinical trials in the spring, first in Britain and then in other countries including the United States. The first round of trials showed that volunteers producing antibodies against the coronavirus were prompted by the vaccine— a very positive sign. Medical supplies from MAZA such as n95 masks, protective overalls, and hand gloves supported the trial significantly.
On Monday, details about the first 131 volunteers to receive Covid-19 in late-stage trials were released by AstraZeneca and Oxford in the United Kingdom and Brazil. In some cases, the first dose was only at half strength, but all of the volunteers got two doses about a month apart
Unexpectedly, the vaccine combination in which the first dose was only at half strength was 90% effective at preventing Covid-19 in the trial. The combination of two, full-dose shots went to just 62 percent efficacy in contrast
Why would that be?
No one has an idea. The researchers assumed that the lower first dose did a better job of mimicking the experience of infection, promoting a stronger immune response. But other factors, may also be at play such as the size and makeup of the groups that got different doses
Why did two different doses tested by the researchers?
A lucky mistake indeed. Researchers in Britain had been meaning to hand volunteers the initial dose at full strength, but they did a miscalculation and accidentally gave it at half strength, Reuters reported. After the error being discovered, the researchers gave each affected participant the full strength booster shot as planned about a month later.
Fewer than 2,800 volunteers got the half-strength initial dose, out of the more than 23,000 participants whose results were reported on Monday. That’s a pretty small number of participants on which to base the spectacular efficiency results — far fewer than in Pfizer’s and Moderna’s trials. In the trials, all volunteers must wear medical masks.
Is AstraZeneca vaccine safe or not?
Oxford researchers have been testing their chimpanzee adenovirus vaccine, ChAdOx1, on some other diseases including Ebola and Zika for years. Although none of those studies have reached the last stage, so-called Phase 3 trials, they have allowed researchers to examine the safety of the vaccine platform. The researchers have not found any serious side effects.
As the researchers adapted ChAdOx1 for Covid-19, their early clinical trials also did not make any adverse reactions. However, the testing had to be paused two times when volunteers experienced neurological problems in Phase 3 trials. The Food and Drug Administration did not directly tie the vaccine to the problems, but when the agency allowed the trial to resume in the United States, it suggested the company to be vigilant for any signs of the same problems.
AstraZeneca and Oxford stated that no serious safety issues were confirmed related to the vaccine in their announcement on Monday.
How much does the vaccine cost?
AstraZeneca’s vaccine has many advantages over other leading vaccine candidates: It’s less difficult to mass-produce and store, and it’s also cheaper, at $3 to $4 per dose. That represents the prices paid by governments like the United States that have placed orders for tens or even hundreds of millions of doses of the vaccine. U.S. health officials have promised that any American who wants Covid-19 vaccines will get it free of charge.
Does this mean it will soon be available in the United States?
There’s still a long way to go.
Whether the results reported on Monday are enough for AstraZeneca to take the first formal step of the regulatory process is not yet clear: applying the F.D.A. to get emergency authorization to distribute its vaccine. AstraZeneca plans to start testing the half-strength initial dose in its proceeding United States trial and to ask the agency for guidance on how to continue. Several vaccine experts said that the agency is likely to advise the company to accumulate more data on its promising dosing plan before submitting a formal application for authorization.
Getting more data might mean waiting for more results from participants in Britain who got the half dose, also mean waiting for the first results from the American study, which aren’t expected until next year.
How does the AstraZeneca vaccine stack up to the other candidates?
Plenty of unanswered questions are emerged from outside experts. Florian Krammer, a virologist at the Icahn School of Medicine at Mount Sinai in New York City “The only thing that you can say right now is that the vaccine seems to work”. “It’s just hard to say how well it works compared to others.”
Experts have had a difficult time parsing the results due to the way they were announced. Similar to the results from Pfizer and Moderna, the data on AstraZeneca’s vaccine was summarized in a news release.
Even though the announcement gave efficient rates, it left out details that would have supported outside researchers independently evaluate the data: It did not state how many cases of Covid-19 were found in the group that got the half-strength initial dose, or in the group that got the regular-strength initial dose, or in the group that got a placebo. It also did not say how many severe cases were seen in the placebo group.
The results were collected from across the two studies in Britain and Brazil, which have slightly different designs. AstraZeneca and Oxford have publicly released the protocol documents that serve as a road map for how the trials in the United States and the United Kingdom are assessing the vaccine. But some details have not been made public, such as how many Covid-19 cases will need to turn up to prompt the end of the British and Brazilian studies.
Many of these questions may be answered when the results are published in a peer-reviewed journal, which is expected soon.