Just hours after the UK jabbed its first citizen against the coronavirus, researchers have confirmed that Oxford’s vaccine is safe and effective in the first peer-reviewed publication of a Phase III coronavirus vaccine trial yet. 

“The results for me are very compelling,” said AstraZeneca’s executive vice president Mene Pangalos on Wednesday at a press conference. “They clearly show that we have an effective vaccine that meets the regulatory standard for approval around the world.”

He added that there were no cases of death, severe COVID-19 or hospitalization in the vaccine arm of the trial; in contrast, the control arm recorded 10 hospitalised COVID-19 cases, two of which were severe, including one death.

The pooled analysis, which was published in The Lancet, was pre-specified and was designed in collaboration with regulatory bodies in the UK, Brazil and Europe. It includes data from four ongoing randomised trials across the UK, Brazil, and South Africa involving almost 24,000 adults, said the head of the Oxford Vaccine Group Andrew Pollard on Wednesday.

“The vaccine is safe, it’s highly effective, and we also know it can be manufactured in large quantities, and at a low price and can feed into existing supply and distribution networks,” Pollard said, speaking at a press conference on Wednesday.

This is probably the best day we’ve had in 2020,” added the Oxford vaccine’s architect Sarah Gilbert on Wednesday, who co-authored the peer-reviewed Lancet report. “It’s a study that’s taken place in three different countries and that’s important.”

Oxford Vaccine Is Safe, But Dosage Regimen Still Unclear 

The interim analysis found that the Oxford vaccine was safe, based on a three and a half month long assessment of 23,745 adults. While 175 severe adverse events were recorded in total, 172 were deemed unlikely to be related to the COVID-19 vaccine – or the placebo  given to the control group. 

There were, however, three events that experts concede may be related to the trials including: one case of haemolytic anaemia in the control group; one case of transverse myelitis in the vaccine group; and one case of severe fever in South Africa in a participant who is still masked to group allocation. On the upside, all three participants are recovering or have already recovered, and are still part of the Oxford vaccine trial.

Nonetheless, the efficacy of the Oxford vaccine is less clear-cut than its safety results, and depends on the vaccine dose that was received. While the “general” pooled efficacy was at 70%, the “minimum” efficacy was at 62% in those that received two standard doses of the vaccine. 

Intriguingly, efficacy rose to 90% in a group that accidentally received half a dose followed by a standard dose – due to an error in the preparation of one large vaccine batch that was used for one group of trial participants. 

In response to a question on the ideal dosage regimen, the vaccine-makers refrained from drafting any recommendations, and have left it in the hands of regulatory agencies to decide for themselves based on the Lancet report. AstraZeneca’s CEO has previously said, however, that a new trial of the lower dose regimen would be undertaken to unequivocally confirm the results and the best dosing protocol. 

“It is entirely up to the regulators to look at the data and decide exactly what they think their label should say [efficacy and dosage regimen] at the end and so that’s sort of in their hands,” said Pollard. 

Even if the minimum efficacy were to be only 62% – almost thirty percentage points lower than Pfizer’s and Moderna’s mRNA vaccines – the Oxford vaccine will still meet the threshold set by major regulators in the UK, Europe and the United States for efficacy, and have a “very important” impact on healthcare systems around the world, emphasized Pangalos. 

At only about US$ 3 per dose, as compared to US$20-US$25, the Oxford vaccine is much cheaper than its mRNA counterparts, and also can be stored at normal refrigeration temperatures, making it particularly suitable for distribution in low- and middle-income countries. 

“It is hard not to be excited about these findings and now the existence of three safe and efficacious COVID-19 vaccines, with 57 more in clinical trials,“ emphasized Maria Deloria Knoll and Chizoba Wonodi from Johns Hopkins Bloomberg School of Public Health in a  joint comment, referring to the results of the Pfizer, Moderna and AstraZeneca trials. 

However, further studies of the AstraZeneca vaccine are needed in more diverse groups – out of the 11,636 people enrolled in ongoing Phase III trials in Brazil and the UK, only 12% were older than 55, and over 80% were white. In addition, all of those volunteers who accidentally received the half-dose regime that appears more effective were under the age of 55.

Image Credits: John Cairns, UK Science Media Centre:.