What are the different types of Respiratory Syncytial Virus (RSV) vaccines, and is MRESVIA PF comparable to RSVPreF3 (Respiratory Syncytial Virus Prefusion vaccine)?

RSV Vaccines: Available Types and Comparability

There are currently three RSV vaccines approved for older adults, and mRESVIA (mRNA-1345) is comparable to RSVPreF3 (Arexvy) in terms of target population and indication, though they use different vaccine technologies. 1

Available RSV Vaccine Types

The three approved RSV vaccines for older adults are:

• RSVPreF3 (Arexvy): A recombinant RSV pre-fusion F protein adjuvanted with AS01E, approved for adults ≥50 years 1
• RSVpreF (Abrysvo): A recombinant bivalent RSV-A and RSV-B pre-fusion F protein (non-adjuvanted), approved for adults ≥60 years 1
• mRESVIA (mRNA-1345): An mRNA-based vaccine, approved for adults ≥60 years 1

Key Differences Between Vaccine Technologies

RSVPreF3 (Arexvy) Characteristics

• Contains AS01E adjuvant, which enhances immune response 2
• Demonstrated 82.6% efficacy against RSV-associated lower respiratory tract disease in the first season 2
• Showed 94.1% efficacy against severe RSV-related lower respiratory tract disease 2
• Maintains efficacy for at least three RSV seasons, though efficacy decreases over time 3
• Cumulative efficacy over three seasons was 62.9% against RSV-LRTD 3
• Only vaccine approved for adults aged 50-59 years with risk factors 4

RSVpreF (Abrysvo) Characteristics

• Non-adjuvanted bivalent formulation 5
• Demonstrated 88.9% efficacy against RSV-associated LRTI with ≥3 symptoms at end of season 1 5
• Showed 77.8% efficacy at end of season 2 5
• Maintains efficacy for at least two RSV seasons 4
• Also approved for maternal immunization during pregnancy (32-36 weeks) 6

mRESVIA (mRNA-1345) Characteristics

• Uses mRNA technology platform 1
• Approved for adults ≥60 years 1
• Limited comparative data available in the provided evidence

Comparability Assessment

mRESVIA and RSVPreF3 are comparable in their approved age indication for adults ≥60 years, but RSVPreF3 has the unique advantage of approval down to age 50 years for high-risk individuals. 1 Both vaccines target the same RSV prefusion F protein antigen, though they use different delivery mechanisms (mRNA versus recombinant protein with adjuvant). 1

Important Clinical Considerations

• All three vaccines are considered interchangeable for adults ≥60 years based on guideline recommendations that do not express preference among available vaccines 4
• For adults aged 50-59 years with risk factors, RSVPreF3 is the only approved option 4, 1
• Both RSVPreF3 and RSVpreF demonstrate high effectiveness (75-82%) against RSV-associated hospitalization in real-world post-licensure studies 4
• The Portuguese guideline explicitly states that "two RSV vaccines are currently available in Portugal" (referring to RSVPreF3 and RSVpreF), suggesting mRESVIA may have more limited availability in some regions 4

Safety Profile Comparison

• Both RSVPreF3 and RSVpreF are generally well tolerated with acceptable safety profiles 4
• Most adverse events are transient and mild-to-moderate in severity 4, 2
• RSVPreF3 is more reactogenic than placebo, with injection-site pain and fatigue being most common 4
• Serious adverse event rates are similar between vaccine and placebo groups for both RSVPreF3 (4.4% vs 4.3%) and RSVpreF (4.3% vs 4.1%) 4
• Post-licensure surveillance has identified potential increased risk for Guillain-Barré syndrome after protein subunit RSV vaccination 1

Practical Pitfalls to Avoid

• Do not assume all three vaccines have identical age indications - only RSVPreF3 is approved for the 50-59 year age group 1
• Do not require extensive documentation of risk factors - patient attestation is sufficient to avoid barriers to vaccination 1
• Be aware that co-administration with influenza vaccines may result in numerically lower antibody titers for both RSV and influenza, though clinical significance is unknown 4, 7