Recommendation
By CDC: >75 y/o, or >60 with risk factors
Vaccines
There are 2 main brands in singapore: Arexvy (GSK) and Abrysvo (Pfizer)
| Feature | Arexvy | Abrysvo |
|---|---|---|
| Manufacturer | GSK | Pfizer |
| Vaccine type | Adjuvanted (AS01E) | Non-adjuvanted, bivalent (RSV A + B) |
| Platform | Recombinant RSV prefusion F protein | Recombinant RSV prefusion F protein (bivalent) |
| Approved for older adults (≥60) | Yes | Yes |
| Approved for high-risk adults <60 | Yes | Yes |
| Approved in pregnancy | No | Yes (32–36 weeks gestation) |
| Infant protection via maternal vaccination | No | Yes (~6 months passive immunity) |
| Dosing | Single IM dose | Single IM dose |
| Overall efficacy (trial data) | ~82–83% | ~67–86% (varies by endpoint) |
| Severe disease efficacy | Up to ~94% | High, but varies by definition |
| Real-world effectiveness | ~77–83% | ~73–79% |
| RSV strain coverage | Covers A & B (not explicitly bivalent) | Explicitly bivalent (A & B) |
| Adjuvant | Yes (AS01E) | No |
| Reactogenicity | Slightly higher (due to adjuvant) | Slightly lower |
| Common side effects | Injection pain, fatigue, headache, myalgia | Injection pain, fatigue, headache, myalgia |
| Notable safety considerations | More local/systemic reactions | Small signal for preterm birth (not proven causal) |
| Best suited for | Older adults wanting stronger immune response | Pregnancy, or preference for non-adjuvanted vaccine |
Monoclonal antibody (mAb): Nirsevimab (Az)
Monoclonal antibody to target RSV Fusion (F) protein, prevents it from binding and entering into cells. It confers passive immunity to infants.
<5 kg → 50 mg
≥5 kg → 100 mg
Recommendation
- Best is for passive immunity from mother: to give Abrysvo to mother at 32-36/52 GA
- If this is missed or given <2/52 of delivery, consider giving catch up infant mAb
- For catch up: normal infants < 8/12 old, at risk infants > 8/12 old
- All at risk infants to receive
Why?
- Reduce risk of severe infant respiratory illness
- ? reduce risk of recurrent wheeze / allergic asthma