AstraZeneca vaccine is effective but leaves questions in older ages

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

The 10 cases of hospitalization seen in the trial all occurred among those given a placebo, suggesting the shot prevents the worst symptoms, according to the results published Tuesday in The Lancet medical journal. Yet the vaccine’s efficacy couldn’t be assessed in older age groups because there weren’t enough infections, 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, director of the Oxford Vaccine Group. “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 sheds more light on the strengths and shortcomings of the inoculation following weeks of confusion surrounding the late-stage trial, but still leaves unanswered questions about its potential role fighting a contagion that has killed more than 1.5 million people. Still, even if the vaccine can’t match the efficacy delivered by front-runners Pfizer Inc. and Moderna Inc., it is expected to be cheaper and easier to deploy far and wide.

Initial Data

Initial data from Astra and Oxford last month 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 discrepancy and only tested in a younger group. Astra 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 Tuesday it’s still deciding whether to hold an additional study.

The results, based on advanced trials of 11,636 people in the U.K. 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 Covid-19 or control vaccines, one case of the neurological disorder transverse myelitis may be linked to the shot, the paper said.

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.

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 Organization to accelerate the delivery of the vaccine to low-income nations.

The lack of clarity over the true efficacy of the Astra-Oxford jab and plans for the additional study aren’t expected to hold up regulatory approvals in the U.K. and European Union, Soriot said last month, with a green light in Britain possible by year-end. U.S. approval won’t come until 2021 after trials there were paused for nearly seven weeks following the incident of suspected transverse myelitis in the U.K. study. The British trial resumed in less than a week.

The Oxford-Astra data will be scrutinized around the world, with many countries counting on the vaccine to protect their populations. The vaccine will cost a fraction of the price set by Pfizer and partner BioNTech SE, and another shot from Moderna, both of which showed 95% efficacy. The Astra shot should also be easier to deploy, with storage temperatures of between two and eight degrees Celsius, compared with minus 70 for Pfizer’s shot.

The results come as the U.K. released the first vaccine in the western world. The Pfizer-BioNTech shot was approved in Britain last week and starting Tuesday is being given 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 US as soon as this week and the EU by the end of the year.