The emergence of the Omicron variant has brought new attention to the hunt for a universal COVID-19 vaccine.
In the latest development, the Coalition for Epidemic Preparedness Innovations (CEPI) is putting money behind an effort to test a potential Omicron vaccine made by a small California biotechnology firm. CEPI is an international public-private partnership that funds research into medicines designed to combat current and future disease outbreaks.
Gritstone Bio, a startup based in Emeryville, Calif., has been working on a COVID-19 vaccine technology that it believes could work against multiple strains of SARS-CoV-2, the virus that causes the disease. CEPI is giving Gritstone up to $5 million to run an initial human clinical trial of its vaccine against the Omicron variant in South Africa.
CEPI previously committed to providing Gritstone with $20.6 million to test a slightly different version of its vaccine against the Beta variant, with preliminary human clinical trials of that vaccine set to begin in South Africa within the coming weeks.
Most existing vaccines work by targeting SARS-CoV-2’s spike protein. But mutations in this spike protein can render existing vaccines less effective.
Gritstone’s version is different from those vaccines already approved in that, in addition to targeting the version of the spike protein for a given coronavirus variant, it also prompts the body to produce other proteins associated with SARS-CoV-2 that can be recognized and targeted by T cells, a part of the immune system that swoops in to destroy virus-infected cells.
Gritstone is targeting virus proteins that are common across all the virus strains, and which don’t seem to mutate often, meaning that these proteins could form the basis of a vaccine that would confer at least some immunity against all coronavirus variants.
Another difference between Gritstone’s vaccines and those already authorized for use against COVID-19 is that Gritstone is using a technology called self-amplifying messenger RNA (SAM). In these vaccines, the mRNA carried into the body’s cells has the ability to replicate. This should, in theory, produce more antigens and a stronger and longer-lasting immune response than is the case with normal mRNA vaccines.
But some virologists are skeptical of Gritstone’s and others’ efforts to produce a universal coronavirus vaccine. They note that decades-long efforts to produce a universal flu vaccine have so far failed. They also point out that in a natural COVID-19 infection, a person’s body mostly produces antibodies to the spike protein and it remains unclear how large a role the T cell response plays. Only spike protein antibodies can prevent cells from being infected in the first place, whereas T cells only act on cells that have already been infected. A strong T cell response may limit the severity of an infection, but it doesn’t stop it from occurring, and it may not help prevent people from spreading the disease to others.
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