Moderna initiates Phase 3 trial for RSV vaccine candidate

By Rachel Arthur

- Last updated on GMT


Related tags Moderna mRNA RSV COVID-19 Vaccines Influenza

Moderna has initiated the Phase 3 portion of its pivotal respiratory syncytial virus (RSV) vaccine trial: looking towards its ultimate goal to combine the vaccine with its COVID-19 and flu boosters into a single dose booster.

The Phase 2/3 trial for the RSV vaccine,mRNA-1345, started in November: with the company announcing today that the Data and Safety Monitoring Board (DSMB) has endorsed the Phase 3 trial in adults 60 years and older. The DSMB's endorsement comes after independent review of preliminary Phase 2 data, which suggest that the vaccine has an acceptable safety profile in older adults at the selected dose.


The RSV vaccine represents one of Moderna’s most advanced mRNA clinical programs, after the approved COVID-19 vaccine and its CMV vaccine, which entered a Phase 3 trial in October.

There is currently no approved vaccine for RSV; yet causes a severe disease burden among older adults and young children where it is the leading cause of severe respiratory illness, including pneumonia and respiratory distress.

RSV causes around 177,000 hospitalizations and 14,000 deaths in adults aged 65+ every year in the US, resulting in an estimated $3bn in annual medical costs.

While RSV tends to be a seasonal illness, the COVID-19 pandemic has led to increased interseasonal RSV infection.

mRNA-1345 is a vaccine against RSV encoding for a prefusion F glycoprotein, which elicits a higher neutralizing antibody response compared to the postfusion state. mRNA-1345 uses the same lipid nanoparticle (LNP) as Moderna's COVID-19 vaccine and contains optimized protein and codon sequences.

In August, the FDA gained Fast Track designation for mRNA-1345 in adults older than 60 years of age. The primary purpose of the Phase 3 segment of the study is to establish the safety and efficacy of mRNA-1345 vaccine in this age group in support of licensure: with Moderna expecting to enroll around 34,000 participants in the study.

Creating a combined RSV, flu and COVID-19 jab

Moderna’s first mRNA vaccine, the Spikevax COVID-19 vaccine, was first authorized by the FDA in December 2020; while a booster vaccine received EUA in November last year.

Its seasonal flu vaccine candidate, mRNA-1010, is preparing to enter Phase 3 trials.

A combined COVID-19 and flu vaccine is already in development; and the company is also looking at how it can combine all three vaccines together.  

Preclinical studies have already shown that the seasonal flu, RSV and COVID-19 booster vaccines can be combined into one dose that produces an immune response to all six antigens.

Related topics Bio Developments Pipelines

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