Oxford Covid vaccine is safe and effective, new data shows

The vaccine developed by the University of Oxford and AstraZeneca is safe and has the best immune response when a full two-dose regimen is used, new trial data shows.

The UK has secured 100 million doses of the jab, which the Medicines and Healthcare products Regulatory Agency (MHRA) is currently considering whether or not to approve.

Detailed new data from phase one and two clinical trials shows the vaccine stimulates a broad range of antibody and T-cell responses, and the paper states that it “strongly supports” the team’s move to a two-dose regimen in ongoing phase three trials.

Findings from phase three trials published in The Lancet earlier this month had previously found that the jab is 90 per cent efficacious if administered at a half dose and then at a full dose, or 62 per cent effective if administered in two full doses. However, more work needs to be done to affirm that result.

The jab had come under scrutiny following the emergence of apparent irregularities in the trial data released in November – when it was revealed that the particularly effective half-dose/full-dose regimen was initially administered in UK trial participants by mistake.

The latest details released on Thursday made no reference to the half-dose/full-dose regime, which Oxford has said had been “unplanned” but approved by regulators in their rolling vaccine reviews.

“This highly detailed analysis of the immune responses to ChAdOx1 nCoV-19 further underpins the potential of this vaccine to induce protection against Covid-19 disease and provides additional reassurance of the safety of this approach,” said Professor Katie Ewer at the University of Oxford.

“Using these advanced immunological techniques, we can better understand the different cellular and antibody-mediated mechanisms that contribute to the protection afforded by this vaccine, as demonstrated in the recent data from the subsequent phase three trials.”

Previous studies have shown that in order to develop any vaccine against coronavirus, two key elements of the immune system need to be activated.

These involve stimulating antibodies against the coronavirus spike protein, as well as robust T-cell responses.

The new findings are reported in two papers, both released in the journal Nature Medicine.

One paper outlines the early-stage planning involved in the design of phase trials to investigate two booster dose schedules – a standard dose followed by a second standard dose and a standard dose followed by a lower dose.

Researchers used data from this to support the change to a two-dose regimen in the ongoing phase three trials.

The booster doses of the vaccine induced stronger antibody responses than a single dose, with the standard dose/standard dose activating the best response – supporting the decision to move to a two-dose vaccine regimen in phase three trials.

The paper also shows that many different antibody functions are triggered by the vaccine that may be important in protecting against the disease.

In the second paper, the authors detail an investigation of the T-cell and antibody responses generated by the vaccine.

The authors report induction of a T-cell subset, known to be particularly effective at clearing virus-infected cells from the body during infection.

This type of T-cell response in combination with the detailed antibody profile is highly favourable for an efficacious vaccine, and further supports the profile of this vaccine as safe, researchers said.

Once seen as the frontrunner in the development of a coronavirus vaccine, the British team has been overtaken by US drugmaker Pfizer, whose jabs have been rolled out in the UK and the US.

However, the UK is eagerly awaiting regulatory approval of the jab – which is significantly easier to store and transport – in order to bolster its supplies and expedite its mass vaccination programme.

Additional reporting by PA