Covid: vaccine booster tackling multiple coronavirus variants shows promise, suggests trial data

A Covid vaccine booster which is aimed at tackling multiple variants of the virus has shown promise in inducing a comprehensive immune response, early data has suggested.

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The first results of a phase one trial, which was launched in Manchester in September 2021, have revealed the vaccine has strong levels of neutralising antibodies.

They are similar to approved mRNA vaccines, such as Pfizer/BioNTech and Moderna, but research indicated they are at up to a 10-fold lower dose in the first 10 individuals.

The jab is being trialled with the anticipated involvement of 20 people aged 60 and over, who were in good health and previously received two doses of the Oxford/AstraZeneca jab.

The vaccine was generally safe and well-tolerated, according to the data.

The jab, which is part of Gritstone’s CORAL programme, is a self-amplifying mRNA second generation SARS-CoV-2 vaccine, which targets both spike and non-spike proteins.

The vaccine candidate also produced broad T-cell responses, which form part of the body’s immune response.

Antibodies bind to the body’s foreign invaders and tell the immune system it needs to take action, but T-cells are a type of white blood cell which hunt down and destroy infected cells in the body.

Current vaccines target the spike protein of the coronavirus, which means variants which have mutations to this part of the virus may be able to escape the immune response induced by the jabs.

The researchers tested a single 10 microgram dose of the vaccine dose administered at least 22 weeks after two doses of the AstraZeneca vaccine, with data suggesting it induced new T-cell responses and demonstrated the potential for variant-proof immunity.

According to the researchers it also induced a boost to pre-existing T-cell responses.

The findings from the trial are published by US-based biotechnology company Gritstone bio, Inc. in collaboration with the University of Manchester and Manchester University NHS Foundation Trust.

Based on the results, which have not yet been peer-reviewed, the trial is being expanded to 120 people.

This is taking place within the National Institute of Health Research Manchester Clinical Research Facility (NIHR Manchester CRF) at Manchester Royal Infirmary, part of Manchester University NHS Foundation Trust (MFT).

‘We believe this vaccine will elicit strong, durable, and broad immune responses’

Professor Andrew Ustianowski, honorary clinical chairman at the University of Manchester and chief investigator for the study, said: “It is increasingly apparent that a focus on T-cell immunity is an important way to generate the robust and durable immunity that may prevent future Sars-CoV-2 variants from causing severe disease, hospitalisation, and death.”

He added: “We know the immune response to first generation vaccines can wane, particularly in older people.

“Coupled with the prevalence of emerging variants, there is a clear need for continued vigilance to keep Covid-19 at bay.

“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.”

Andrew Allen, co-founder, president and chief executive officer of Gritstone, said: “This innovation enables inclusion of a wide array of highly conserved viral epitopes, potentially creating an immune state that may offer more robust clinical protection against current and future Sars-CoV-2 variants and be a first step toward developing a pan-coronavirus vaccine.”

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