Yet another coronavirus vaccine frontrunner has announced positive results, increasing hopes for global immunization programs in 2021.
At 70 percent protection, the efficacy of the eagerly-awaited vaccine from Oxford University and AstraZeneca may not, on the face of it, look as good as the two previous vaccines that have posted results in recent weeks. Moderna and the Pfizer/BioNTech both reported efficacy of over 90 percent in large-scale trials.
But data from the Oxford/AstraZeneca trial suggests that that by tweaking the dosage regimen they can improve on the 70 percent figure. And the vaccine has other advantages, with simpler cold storage requirements and a more tried and tested underlying technology behind it.
According to an interim analysis from a large scale phase 3 clinical trial conducted in the U.K. and Brazil, the efficacy of the Oxford/AstraZeneca vaccine depends on how it is administered. Results from nearly 9,000 people given two full doses of the vaccine at least one month apart demonstrated 62 percent protection against infection. But results from a smaller group of 2,741 people who were given a half dose and then a full dose — again one month apart — were even better, with 90 percent protection. Combining the data from the two arms of the trial produced an overall efficacy for the vaccine of 70 percent.
If the regimen of a half dose plus full dose is approved by regulators, that would have the added advantage of allowing many more people to be vaccinated with the current planned supply.
As to why the latter combination may be more effective even though it involves less of the vaccine, Andrew Pollard, chief investigator of the Oxford Vaccine Trial, explained to journalists Monday that this result could reflect the “priming” the immune system.
Another reason, put forth by Sarah Gilbert, leader of the University of Oxford team: The finding may be a result of the dosing better mimicking real infection. However, the scientists don’t yet know whether this is a difference in the quality or the quantity of the immune response. Further data is expected next month, but Pollard said there was no reason to think that it would substantially change the current figures.
Another encouraging sign from the trial is that while there were 131 COVID-19 cases in the trial sample, but there were no hospitalized or severe cases in anyone who received the vaccine, suggesting it may offer some protection even in people who do become infected.
Unlike Moderna and Pfizer/BioNTech which have deployed a never before used mRNA technology in their candidate vaccines, AstraZeneca/Oxford’s jab is a more standard viral vector vaccine — it is based on a weakened version of the common cold virus that contains genetic material from the novel coronavirus. That means it can be stored at two to eight degrees Celsius and distributed using existing logistics — a big advantage when rolling out vaccines at vast scale.
Richard Hatchett, CEO of the Center for Epidemic Preparedness Innovations (CEPI), a foundation that funds vaccine development, said that the success of phase 3 trial was a “significant step” towards “multiple safe and effective vaccines to control the pandemic in a range of populations and settings.”
Similarly, World Health Organization Director General Tedros Adhanom Ghebreyesus said today that the vaccine announcements provide “real hope that vaccines in combination with tried and tested public health measures will help to end the pandemic.”
However, Pollard cautioned against making outright comparisons between the vaccines, pointing to the differences in what exactly was being measured. In the case of the AstraZeneca/Oxford vaccine, for example, researchers included everything from mild to severe cases.
Another variable is when the trial began.
Azra Ghani, chair in Infectious Disease Epidemiology at Imperial College London, said that while the Moderna and Pfizer/BioNTech trials began recruitment in July, the AstraZeneca/Oxford trial started recruitment in May. This means that AstraZeneca/Oxford have had more time for follow-up and for participants to contract coronavirus.
“Once final data are available across all three trials, it would be helpful to undertake a combined analysis to fully understand any differences in efficacy across difference population groups,” said Ghani.
After the news release, AstraZeneca said it would prepare to send the data to regulators for conditional or early approval.
Researchers, meanwhile, are currently submitting data to the European Medicines Agency and the U.K.’s Medicines and Healthcare products Regulatory Agency on a rolling basis. They’re also planning to seek an emergency use listing from the World Health Organization, which would ensure that the vaccine could be distributed in low-income countries.
The ability to more easily distribute a vaccine that can be easily stored in ordinary fridge temperatures — rather than in a deep freeze — is significant. Peter Piot, special adviser to European Commission president Ursula von der Leyen and director of the London School of Hygiene and Tropical Medicine, said this feature would “help with equitable access all over the world.”
In comparison, the Pfizer/BioNTech vaccine needs to be kept at minus 70 degrees Celsius — a requirement that may prevent distribution in many countries.
The AstraZeneca/Oxford vaccine is also significantly cheaper than its mRNA counterparts. Moderna’s candidate could be sold in the range of $32 to $37 per dose. By contrast the AstraZeneca/Oxford vaccine will be sold at cost until the end of the pandemic (reportedly limited to July 2021) — around €2 per dose.
As for plans for global distribution, Pam Cheng, executive vice president of operations and information technology at AstraZeneca, said that at the end of the first quarter in 2021, there should be over 300 million doses available globally if the full dose were given. This amount doesn’t include the additional capacity from several partners that will also be producing the jab, including the Serum Institute of India, the world’s biggest manufacturer by doses sold.
Scientists expressed optimism about today’s announcement, while U.K. Health Secretary Matt Hancock told Sky News that the U.K. has “100 million doses on order and should all that go well, the bulk of the rollout will be in the new year.” The European Commission has agreed a contract to purchase 300 million doses, with an option for 100 million more.
But many also urged caution.
“There are still many hurdles to cross before this pandemic is under control and we can return to normal life,” said Piot. He called for people to continue to follow rules to prevent the spread of the virus until “we see the full and widespread impact of vaccination.”
Even U.K. Prime Minister Boris Johnson had a note of caution when he tweeted: “Incredibly exciting news the Oxford vaccine has proved so effective in trials. There are still further safety checks ahead, but these are fantastic results.”
Other experts pointed to the need to see the detailed data underpinning the announcement, including information on efficacy across age groups.
Data from the phase 2 trial of the AstraZeneca/Oxford vaccine published in the Lancet last week, indicated that the vaccine appeared to be safe in older adults, prompting a similar immune response in this age group as it does in younger people.
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