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Early data for multivariant COVID-19 vaccine booster shows promise

Gritstone COVID-19 Vaccine Booster Study

The first results of an early trial of a multivariant COVID-19 vaccine booster, launched in September 2021 and supported by the NIHR, has released positive data.

US-based biotechnology company Gritstone bio, Inc. in collaboration with The University of Manchester and Manchester University NHS Foundation Trust have announced the initial phase one clinical data shows the vaccine has strong levels of neutralising antibodies. These are similar to approved mRNA vaccines, but up to a 10-fold lower dose in the first 10 individuals.

Results also show the vaccine, which 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 AstraZeneca's first-generation COVID-19 vaccine, was generally safe and well-tolerated.

Part of Gritstone’s CORAL program, the compound is a self-amplifying mRNA second generation SARS-CoV-2 vaccine – or samRNA for short – which delivers antigens from both spike and non-spike proteins.

The samRNA vaccine also produced broad CD8+ T cell responses against targets from conserved SARS-CoV-2 viral proteins and boosted spike-specific T cells.

Based on results, the trial is now being expanded to 120 people, potentially enabling more rapid advancement into a later stage trial.

The trial 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). At MFT, the trial is being delivered by the Research and Innovation Vaccine Team. The trial is also supported by Health Innovation Manchester.

The study vaccine demonstrated a well-tolerated safety profile, with no severe adverse events or unexpected safety events.

Professor Andrew Ustianowski, National Clinical Lead for the NIHR COVID Vaccine Research Programme, is the Chief Investigator for the study at MFT.

Professor Ustianowski said: “These initial data with Gritstone’s innovative samRNA COVID program strongly support its unique approach of CD8+ T cell priming and potent neutralising antibody generation with a dose of samRNA potentially up to 10-fold lower than that required for first generation mRNA vaccines. 

“We are excited to announce the expansion of the footprint of this trial from an initial 20 people to 120 and are looking forward to continuing this work with Gritstone in the clinical development of this promising next generation, T cell enhanced COVID-19 vaccine.

“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 critical in maintaining protection of this vulnerable elderly population who are particularly at risk of hospitalisation and death.”

More information on the study’s initial results can be found on the Manchester University NHS Foundation Trust website.

Immunogenicity and reactogenicity data for additional cohorts is anticipated in coming months.

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