Gritstone bio trumpets first data for ‘multivariant’ COVID jab

by Stephen Riddle

A COVID-19 vaccine that could work against multiple variants of the coronavirus – developed by US biotech Gritstone bio – has generated encouraging immune response data in its first clinical trial.

The new vaccine differs from the currently approved shots because it delivers antigens for both the spike protein and other proteins found in SARS-CoV-2.

That could mean it is less susceptible to the loss of efficacy to vaccines that can occur when there are changes in the spoke protein – as witnessed with the new Omicron variant.

The results of the CORAL-BOOST are only in a few patients, but showed strong increases in neutralising antibody levels when Gritstone’s shot given as a booster after two doses of AstraZeneca’s Vaxzevria given as a primary course.

It also stimulated broad CD8+ T cell responses against the non-spike proteins, and boosted pre-existing responses against spike generated by AZ’s jab.

The focus on non-spike proteins is important “because the other proteins differ much less between the variants of SARS-CoV-2 than the spike protein, so we would expect a better degree of cross-protection against different variants,” commented Prof Charles Bangham, an immunology specialist at Imperial College London, who wasn’t involved in the trial.

Gritstone’s candidate is a self-amplifying messenger RNA vaccine (samRNA), which uses a slightly different technology to the mRNA-based jabs from Pfizer/BioNTech and Moderna.

samRNA vaccines instruct the body to make large amounts of mRNA, which in turn generates the protein antigens, and that means only a small dose is necessary, stretching supplies further.

It will now move into a larger 120-patient stage of the study, with the hope of advancing quickly into pivotal trials and getting a green light for use in booster campaigns.

The study in 20 people aged over 60 was run by the National Institute of Health Research Manchester Clinical Research Facility (NIHR Manchester CRF). Lead investigator Prof Andrew Ustianowski said the results are important because it is increasingly apparent that T cell immunity is an important factor in generating durable immunity with COVID-19 vaccines.

“We believe this vaccine, as a booster, will elicit strong, durable, and broad immune responses, which may well be likely to be critical in maintaining protection of this vulnerable elderly population who are particularly at risk of hospitalisation and death,” he said.

Another commentator, retired consultant in communicable disease control Dr Peter English, said while it is hard to gauge the significance of the results yet, they are encouraging.

“With new variants – like Omicron and B.1.640.2 – constantly evolving, vaccines that can more effectively prevent illness caused by variants of the virus may well have a place in our future armoury,” he added.

“Whether this particular vaccine will be such a vaccine – or will make it to market, be approved by regulators, and be widely used – will not become clear for some time,” continued English.

“But it may be; and if it doesn’t other novel vaccines with similar benefits may well take on this role.”

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