Trials start of vaccine adjusted for variants

AstraZeneca testing a new jab that has been modified to meet changing needs

Researchers in the United Kingdom are testing a new version of the COVID-19 vaccine from Oxford University and AstraZeneca that has been altered in order to provide better protection against variants of the novel coronavirus.

The new vaccine, which is called AZD2816, is closely based on the original AstraZeneca jab, with minor genetic alterations in order to increase efficacy against the Beta strain of the virus that was first identified in South Africa.

Oxford researchers say that other variants share some of the same mutations seen in Beta, so AZD2816 could provide protection against multiple strains.

Late-stage trials for the new jab started on Sunday, when the first of an eventual 2,250 participants in the UK, South Africa, Brazil and Poland received treatment.

Researchers are initially testing the shot as a booster among participants who have already received a full course of the original AstraZeneca jab or an mRNA treatment, and further testing on unvaccinated people will follow.

"It is important we continue to stay ahead of genetically distinct variants of the coronavirus," said Mene Pangalos, who is executive vice-president of biopharmaceutical research and development at AstraZeneca. "AZD2816 should help broaden individuals' immune response against emerging variants of concern. Initiating the Phase II/III trial for AZD2816 means we can be prepared, should a variant vaccine be required in the future."

Results from the study should come through toward the end of the year.

The AstraZeneca vaccine works by delivering a harmless virus, called a viral vector, into the body's cells. The vector contains genetic information that instructs cells to produce the spike protein which is found on the surface of the novel coronavirus. This familiarizes the immune system with the spike protein, so the body can react and neutralize the virus before infection takes hold.

Over the course of the pandemic, the novel coronavirus has evolved into a variety of strains, many of which have mutations to the spike protein. Some of these changes have made variants more infectious, and some mean that original vaccines are less effective at priming the immune system against a viral invasion.

Researchers at Oxford identified 10 mutations on the spike protein of the Beta variant, and adjusted the genetic instructions contained within the AZD2816 viral vectors accordingly. Many of the mutations in the Beta strain are seen in other so-called variants of concern, the researchers said, so the new jab could provide increased efficacy against other forms of the virus.

"Testing booster doses of existing vaccines and new variant vaccines is important to ensure we are best prepared to stay ahead of the coronavirus pandemic, should their use be needed," said Andrew Pollard, who is director of the Oxford Vaccine Group.

A separate recent study has found that current vaccines may be less effective against the Delta variant, which is currently the most prevalent strain in the UK.

Public Health England found that the Pfizer and AstraZeneca vaccines are 33 percent effective at preventing symptomatic disease from the Delta variant three weeks after a single dose, compared to 50 percent against the Alpha variant, which had previously been dominant in the UK.

Efficacy against the Delta variant rose markedly for both vaccines in the weeks following a second dose. A full course of the Pfizer jab was 88 percent effective at preventing symptomatic infection from the Beta variant and 93 percent effective against the Alpha variant, the study found. Two doses of AstraZeneca were 60 percent effective against the Beta strain, as opposed to 66 percent with the Alpha variant.