Moderna Stock Is Climbing on Trial Data. A Flu-Covid Vaccine Isn’t a Sure Thing.

Moderna said its flu-and-Covid vaccine candidate showed “positive results” in patients aged 50 and over in a late-stage trial. (Adam Glanzman/Bloomberg)

An influenza vaccine candidate from Moderna showed promising results in a late-stage trial, bringing the drug maker one step closer to producing a combined flu-and-Covid shot. But as scrutiny builds around the crucial mRNA technology, producing the first vaccine of its kind won’t be easy.

Moderna said its seasonal flu vaccine candidate, mRNA-1010, showed “positive results” in a Phase 3 efficacy study comparing it with a licensed standard-dose seasonal flu vaccine. Efficacy was 26.6% higher than the licensed vaccine in adults aged 50 and over, the company said in a press release.

Subsequent analyses showed similar results across age groups, risk factors, and previous flu-shot status. In participants aged 65 years and older, mRNA-1010 had a relative vaccine efficacy rate of 27.4%, Moderna said.

The company’s targeting of older adults, who typically have weaker immune systems, makes sense in the context of the most recent flu season. The Centers for Disease Control and Prevention estimate 27,000 to 130,000 flu-related deaths have occurred in the U.S. since October. This compares to 27,965 deaths in the last flu season, at the low end of that range.

“The severity of this past flu season underscores the need for more-effective vaccines,” Moderna CEO Stéphane Bancel said in a statement. In addition to better matching circulating strains, an mRNA-based flu vaccine “could also pave the way for Covid-19 combination vaccines,” he added.

While vaccines don’t prevent illness, they help the body fight infection by promoting the creation of antibodies, or proteins that target foreign substances. Unlike traditional vaccines, which contain weakened versions of a virus, mRNA vaccines include ribonucleic acid, which instructs the immune system how to recognize and defend against viral proteins.

The technology proved its potential during the Covid-19 pandemic, when mRNA vaccines were deployed quickly and widely. Researchers estimate that Covid vaccines prevented millions of deaths worldwide in the first year of the pandemic alone.

Moderna has had its sights trained on a combination vaccine for years now. The company shared encouraging trial data for a candidate called mRNA-1083 in June 2024. The last update came in May of this year, when the company said it had voluntarily withdrawn its pending Biologics License Application, and planned to resubmit after efficacy data for mRNA-1010 became available.

It’s worth noting that mRNA vaccines haven’t always been out of favor with the Trump administration. President Donald Trump himself referred to mRNA vaccines as the “gold standard” at the height of the pandemic. However, the technology has become the target of increasing scrutiny during his second term, specifically under the oversight of Health and Human Services Secretary Robert F. Kennedy Jr.

Kennedy has lambasted mRNA vaccines as unsafe on several occasions and once asserted that they “don’t work at all” in a social media post. Moderna, in particular, has found itself in the crosshairs of Kennedy’s skepticism. Last month, the HHS canceled a contract awarded to the drug maker to develop an mRNA vaccine for bird flu, arguing that the technology “remains under-tested.”

The regulatory environment is still taking shape. In May, the CDC removed Covid-19 vaccine guidance for pregnant women. And just last week, a group of advisors picked by Kennedy said they were forming a work group to evaluate impacts of the children’s vaccine schedule.

While Moderna’s efforts largely concentrate on ensuring the efficacy of mRNA vaccines in older adults, it isn’t far-fetched to assume the company will make the shot available to other groups over time. It is unclear just how much the shifting landscape will compromise these plans. For now, the drug maker says it plans to work with regulators on filing submissions for mRNA-1010.

Shares of Moderna rose 2.4% to $27.82 on Monday. The benchmark S&P 500 and Nasdaq Composite were each up 0.2%.

Write to Mackenzie Tatananni at mackenzie.tatananni@barrons.com