A vaccine developed by the University of Oxford and AstraZeneca provided protection against severe Covid-19, a peer-reviewed study found, though more analysis will be needed to see how well it works in older people, among those at highest risk in the pandemic.

Trial results published on Tuesday in The Lancet medical journal suggest that the shot prevents the worst symptoms. Yet the vaccine’s efficacy couldn’t be assessed in older age groups, the data show.

Because older adults were recruited to the studies later than younger ones, “they’ve had less time for cases to accrue in those age groups and for us to be able to measure an efficacy signal”, said Andrew Pollard, lead investigator on the Oxford trial. “The evidence we have so far on the immune response very much suggests that it’s likely to be similar levels of protection across the ages.”

The report came on the same day that Britain began inoculating its population against the disease, the first Western country to do so, using a vaccine developed by Pfizer and BioNTech. Governments are desperate to overcome the contagion, which has taken more than 1.5-million lives and devastated economies.

While the Astra-Oxford shot looks to be less effective than those of Pfizer-BioNTech and Moderna, it’s expected to be cheaper and easier to deploy worldwide. The Lancet report provides the first peer-reviewed data from any of the leading vaccines.

The initial data from Astra and Oxford in November appeared positive but raised concern over how much protection the shot would offer after the trials produced two different results from two dosing regimens. The partners said their vaccine was 90% effective when a half-dose was given before a full-dose booster, and that two full doses showed an efficacy of 62%.

It later emerged the lower dose was the result of a manufacturing mistake and only tested in a younger group. AstraZeneca CEO Pascal Soriot said in an interview last month the company would set up an additional, probably global, trial to verify the 90% result. The company said on Tuesday it’s still deciding whether to hold an additional study, while Pollard said Oxford had no plans for an extra UK trial at present.

“In terms of which dosing regime, they may make decisions that are specific,” Pollard said in an interview in response to questions about what dose regulators may recommend. “It’s up to policymakers to decide how to use the vaccine once it’s approved.”

While the efficacy rate may be enough to get the vaccine approved, the variability of the rate in different subgroups and lack of data for older people should give regulators pause in rushing this through, according to Bloomberg Intelligence analyst Sam Fazeli.

“I would wait until at least the US trial, which is much more tightly controlled in terms of dosing and intervals between doses, reads out before approving the vaccine,” said Fazeli.

The results, based on advanced trials of 11,636 people in the UK and Brazil, were reviewed after 131 participants contracted Covid-19. Of those, 30 were in the group that received the vaccine and 101 in the control arm, equating to an efficacy rate of 70%, according to The Lancet data.

While the vast majority of 175 severe adverse events were deemed unrelated to the Covid-19 or control shots, one case of the neurological disorder transverse myelitis may be linked to the shot, the paper said.

AstraZeneca shares rose as much as 1.3% after the release of the Lancet report, and closed 0.8% higher in London.

Additional analysis

Further trials to substantiate the unexpected findings and an investigation of efficacy in older adults are needed, Maria Deloria Knoll and Chizoba Wonodi of the Johns Hopkins Bloomberg School of Public Health wrote in an article accompanying the data.

The authors noted “limitations” with the results, including less than 4% of participants who were older than 70 years of age, as well as the finding that no participants older than 55 received the mixed-dose regimen. Still, they said that the expected lower price of the vaccine holds promise for lower- and middle-income nations.

“Despite the outstanding questions and challenges in delivering these vaccines, it is hard not to be excited about these findings and the existence of three safe and efficacious Covid-19 vaccines,” they wrote.

The vaccine showed only a limited ability to prevent transmission of the disease, even though it stopped a majority of those infected from becoming ill.

AstraZeneca has started to submit the data to regulators around the world for early approval and it is ready to begin delivering hundreds of millions of doses, the company said in a statement. The drugmaker said it is also seeking an emergency-use listing from the World Health Organisation to accelerate the delivery of the vaccine to low-income nations.

The lack of clarity over the true efficacy of the AstraZeneca-Oxford jab and plans for the additional study aren’t expected to hold up regulatory approvals in the UK and European Union, Soriot said in November, with a green light in Britain possible by year-end.

US approval won’t come until 2021, after trials there were paused for nearly seven weeks after the incident of suspected transverse myelitis in the UK study. The British trial resumed in less than a week.

The Oxford-AstraZeneca data will be scrutinised around the world, with many countries counting on the vaccine to protect their populations. It will cost a fraction of the price set by Pfizer and BioNTech, and another shot from Moderna, both of which showed 95% efficacy. The AstraZeneca shot should also be easier to deploy, with storage temperatures of between 2°C and 8°C, compared with -70°C for Pfizer’s shot.

The Pfizer-BioNTech shot was approved in Britain last week and is being given first to people over 80 and those in care homes, including workers, before being rolled out more broadly over the coming months. The jab could also be approved in the U.S. as soon as this week and the EU by the end of the year.


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