Moderna’s multi-strain COVID-19 vaccine shows real promise

While US health officials are still debating the best way forward when it comes to boosters for COVID-19 vaccines, one thing was clear when experts convened by the Food and Drug Administration (FDA) recently met for a committee discussion: to For longer and stronger immune responses, the next booster may need to target more than one strain of SARS-CoV-2. That would make COVID-19 vaccines similar to the annual flu shot, which normally helps the body generate immunity against up to three different flu strains.

On April 19, Moderna, which is making one of two mRNA vaccines available in the US, reported the results of the first such combination vaccine. The results have been published on a pre-print server and have not yet been peer-reviewed.

In the study, which involved nearly 900 people vaccinated with a primary series of two doses of Moderna’s original vaccine, they received a booster of the new vaccine at least six months after the first injections. About 300 people received a half-dose booster and nearly 600 received a full dose of the new injection. The new vaccine contained equal amounts of viral genetic material that would help the body’s immune cells produce antibodies against both the original version of the virus and beta, one of several variants that have emerged over the past two years. Another 171 people served as the comparison group and received the original vaccine, with half the dose as the primary series, as a booster dose — as currently recommended by the FDA and the Centers for Disease Control and Prevention.

In general, the combination booster generated higher antibody responses than those produced by the original booster, not only against the original virus strain, but also others, including Delta and Omicron, although the new vaccine did not target those and was designed to target to focus on beta. specifically. Such cross-reactivity is an encouraging sign that combining different strains can elicit a more robust immune response against a number of different variants. With regard to Omicron in particular, at half the dose of the original primary series, containing genetic information from both the original virus and beta variant, the new booster generated more than twice as many antibodies compared to the original booster. – even up to six months after the shot. The full dose generated more antibodies, but also slightly more side effects.

While antibodies contribute only to one type of immunity provided by vaccines, they are important in reducing the risk of being infected with the virus and decreasing the chance of developing severe symptoms of COVID-19.

The half-dose of the new vaccine was not associated with more side effects than the currently approved half-dose booster against the original strain. However, the full dose of the new vaccine was linked to a slightly higher risk of side effects, comparable to the full dose of the original booster, which reversed the company’s previous decision to authorize the original booster at half the dose of the primary. series.

While the results of the latest study are promising, Moderna is also studying a combination booster targeting Omicron and the original strain. Those results are expected later this spring. Given the prevalence of Omicron and its BA.2 subvariant around the world, the company’s scientists anticipate that the combined Omicron booster may be a stronger candidate for consideration as the US’s next booster shot in the fall, but that decision will only be made before the results of that investigation are available.

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