Vaccine for Birth Defects Didn’t Work Well, Won’t Be Continued: Moderna

The vaccine targeted a virus linked to birth defects.

A sign marks the headquarters of vaccine maker Moderna in Cambridge, Mass., on April 28, 2022. Brian Snyder/Reuters

Moderna on Oct. 22 said its vaccine for cytomegalovirus (CMV) did not perform well in a clinical trial.

The investigational shot did not meet the primary efficacy endpoint in preventing CMV infection in healthy females of childbearing age, or aged 16 to 40, Moderna said.

The phase 3 randomized, placebo-controlled trial involved about 7,500 women across approximately 300 sites in 13 countries, including Finland, Israel, and the United States.

The vaccine was developed to prevent CMV, which pregnant mothers can pass to their babies. About one in 200 babies in the United States is born with CMV, and about 20 percent of babies born with the virus have birth defects or long-term health problems such as hearing loss, according to the Centers for Disease Control and Prevention.

Moderna’s CMV vaccine utilizes messenger ribonucleic acid (mRNA) technology, just like its only approved shots, which target COVID-19.

Moderna executives said in January that the trial for the CMV vaccine, mRNA-1647, needed to keep going because interim results did not show enough efficacy, but expressed optimism that the shot would ultimately be successful, noting it could be the first such vaccine on the market because no others exist as of yet.

The efficacy of the shot turned out to be between 6 percent and 23 percent, depending on the case definition.

“We are clearly disappointed by the failure to prevent primary infection because it means there is still no vaccine for the prevention of congenital CMV despite the many decades of work by the field,” Dr. Stephen Hoge, Moderna’s president, said in a statement.

The company has decided to discontinue its CMV program.

Moderna said that the vaccine was “generally well-tolerated ... with a safety profile consistent with earlier studies.” It will continue studying mRNA-1647 in bone marrow transplant patients.

“CMV does cause significant disease in other contexts, including reactivation of the latent virus in those undergoing bone marrow transplantation, and we will continue to explore the potential of mRNA-1647 to suppress disease associated with reactivation in those high-risk patients through our ongoing Phase 2 study,” Hoge said.

That study started in 2023 and is scheduled to be completed in 2026. About 224 people were set to receive the vaccine or placebo after ceasing prophylactic treatment for CMV, including the drug letermovir.

Moderna said its 2025 financial outbreak is not expected to be impacted by the trial failure.

“Moderna anticipated minimal initial revenue contribution from mRNA-1647 given necessary investments in market building and launch,” it stated.

Moderna still expects to break even in 2028.