WWhile U.S. officials remain divided on the best approach to COVID-19 vaccine boosters in the United States, there was one clear message from experts at the Food and Drug Administration (FDA), who discussed that the next booster may need to be more effective and last longer. This would mean that COVID-19 vaccines could be similar to an annual flu shot which helps to build immunity to up to three influenza strains.
Moderna (which makes one of two mRNA vaccinations in the U.S.), published the first results from a combination vaccine. They were posted on a preprint server but haven’t been peer-reviewed.
In the study, which involved nearly 900 people who had been vaccinated with a primary series of two doses of Moderna’s original vaccine, received a booster of the new vaccine at least six months after the initial shots. A half-dose booster was given to 300 and a full dose for 600. 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 against 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, at half the dose as the primary series, as a booster dose—as currently recommended by the FDA and Centers for Disease Control and Prevention.
The combination booster produced higher antibody responses against the original strain of the virus than the booster for other viruses, such as Omicron and Delta, even though it did not specifically target Omicron and Omicron. Cross-reactivity between different strains is a positive sign that you may get a stronger immune response to a variety of variants. With respect to Omicron in particular, the new booster, at half the dose of the original primary series, containing genetic information from both the original virus and Beta variant generated more than twice as many antibodies compared to the original booster—even up to six months after the shot. Although the full dose produced more antibodies but had slightly higher incidences of adverse reactions, it was still less effective.
Although antibodies are only one form of immune system provided by vaccines they can be important in lowering your risk of contracting the virus and reducing your chances of suffering severe COVID-19 symptoms.
The half dose of the new vaccine wasn’t associated with any more adverse events than the currently authorized half-dose booster against the original strain. The full dose of the new vaccine, however, was linked to a slightly higher risk of side effects, similar to the full dose of the original booster, reinforcing the company’s previous decision to request authorization of its original booster at half the dose of the primary series.
Moderna continues to study a booster combination that can target Omicron as well as the original strain. The latest results are encouraging. They are due to be released in the coming weeks. Given the prevalence of Omicron and its subvariant BA.2 around the world, the company’s scientists expect that the combined Omicron booster might be a stronger candidate for consideration as the U.S.’s next booster shot in the fall, but that decision won’t be made until the results of that study are available.
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