Dive Brief:
- Moderna said on Thursday its experimental flu vaccine sparked a strong enough immune response against only one of two groups of influenza strains it was tested against in a Phase 3 trial.
- According to Moderna, its messenger RNA vaccine outperformed existing shots when tested against the A strains of influenza — the most common form of flu — but didn’t match available vaccines against the less prevalent B strains. Moderna also noted a higher rate of side effects in those who received its shot, though those adverse reactions were largely graded as mild.
- The findings set back Moderna’s plans to prove that mRNA shots can produce superior vaccines for flu. The company still has another trial underway, however, that will test how well the shot can prevent disease. Pfizer and partner BioNTech also have an mRNA-based flu vaccine in late-stage testing.
Dive Insight:
mRNA vaccine developers are coming off a string of successes against COVID-19 and, more recently, respiratory syncytial virus. But the bar is higher in flu, where multiple existing shots are already available.
Vaccine makers like Moderna have argued that advantages in speed and manufacturing will allow them to better tailor their shots to a given year’s prominent strains and make more effective vaccines. Moderna’s trial was a key test of those assertions, and the results left some analysts and investors underwhelmed.
The trial tested Moderna’s shot, mRNA-1010, in more than 6,000 adults in the Southern Hemisphere and was designed to evaluate the immune response it generated, as well as its safety profile. The vaccine met its goal against A/H1N1 and A/H3N2 strains, surpassing available vaccines. But it failed to hit its mark against B/Victoria and B/Yamagata-lineage strains, for which it couldn’t match existing shots.
Adverse event rates were also higher, with 70% of those receiving Moderna’s shot reporting a side effect, compared to 48% of those who received a different vaccine. The most common side effects were pain and swelling.
Moderna, for its part, argued that the A strains of the virus lead to a majority of flu-related disease and hospitalizations. It also noted that it has quickly tweaked its shot to produce stronger results against B strains.
Additionally, a second large trial in the Northern Hemisphere is ongoing, with interim results expected this quarter. In that study, 200 participants had confirmed cases of the flu, and more than 99% of them were infected with an A strain of the virus.
Nonetheless, investors and analysts reacted negatively to the results. Moderna shares sank by 5% in midday trading Friday. SVB Securities analyst Mani Foroohar, meanwhile, noted that “only significantly superior efficacy results would justify use” of Moderna’s shot given the number of available alternatives.
“We are not surprised to see shares trading off modestly,” Foroohar wrote.
mRNA-1010 is one of five experimental mRNA candidates for flu being tested by Moderna.