Moderna announced last week that it began testing its seasonal flu mRNA vaccine as part of an early-stage study to develop combination vaccines that would target multiple respiratory viruses.

The flu and current vaccines

According to the World Health Organization (WHO), approximately 3 million severe cases of flu occur globally each year, which result in between 290,000 to 650,000 flu-related deaths.

In the United States, CDC data shows that an average of 8% of the U.S. population experiences flu symptoms every year. And according to a 2018 study from NIH, the average yearly economic burden of the flu is around $11.2 billion.

According to Moderna, currently available flu vaccines are only around 40% to 60% effective at protecting against common influenza viruses and their formulations must be finalized between six and nine months in advance. Additionally, Moderna said, the egg-based production method that the majority of flu vaccines use may lead to unintentional antigenic changes to the virus.

The potential of mRNA vaccines

For the Phase 1/2 trial, Moderna is testing an mRNA vaccine—created using the same mRNA technology the company used to create its Covid-19 vaccine—on approximately 180 healthy adult participants 18 years and older. The vaccine targets influenza lineages recommended by WHO. 

Moderna's CEO Stéphane Bancel said the company believes mRNA vaccines have several advantages, including "the ability to combine different antigens to protect against multiple viruses and the ability to rapidly respond to the evolution of respiratory viruses, such as influenza, SARS-CoV-2 and [respiratory syncytial virus] RSV."

In a statement, the company said its overarching seasonal flu program aims to develop vaccines with different antigen combinations and test them against seasonal flu viruses. Moderna also plans to develop a potential combination vaccine that would protect people against the seasonal flu, coronavirus variants, and RSV.

"Our vision is to develop an mRNA combination vaccine so that people can get one shot each fall for high efficacy protection against the most problematic respiratory viruses," Bancel said. (Doherty, Axios, 7/7; Moderna press release, 7/7; Sullivan, The Hill, 7/7)