Preventing respiratory syncytial virus in older adults

Clinical question

How effective and safe is respiratory syncytial virus (RSV) vaccination in older adults?

Bottom line

For roughly every 380 medically stable patients (≥60 years), RSV vaccination prevents 1 RSV-associated lower respiratory tract disease (LRTD) per season (vs placebo). Fatigue occurs in 34% of patients (vs 16% placebo). Guidance suggests administering based on shared decision making, mainly in those at higher risk.

Evidence

Results were statistically different unless indicated.

• An RCT¹ (24,966 adults ≥60 years) compared single-dose adjuvanted RSV prefusion F protein vaccine (RSVPreF3OA [Arexvy]) with placebo. Results were presented after the first RSV season (6.7 months):

  • - Cases of RSV-LRTD: 0.06% vs 0.3% (placebo); number needed to vaccinate (NNV)=379.

  • - Severe (>2 clinical signs or investigator-assessed) cases: 0.008% vs 0.1% (placebo); NNV=781.

  • - Injection site pain in 61% versus 9%, and fatigue in 34% versus 16%, but no statistics were provided.

• An RCT² (34,284 adults ≥60 years) compared single-dose unadjuvanted RSV prefusion F protein vaccine (RSVpreF [Abrysvo]) with placebo. Results were reported after the first RSV season (7 months):

  • - Cases of RSV-LRTD (≥2 signs or symptoms): 0.07% vs 0.2% (placebo); NNV=742.

  • - Cases of RSV-LRTD (>3 signs or symptoms): 0.01% vs 0.08% (placebo); NNV=1360.

  • - Local reactions: 12% vs 7% (no statistics provided).

• In a systematic review³ of published and unpublished data of 2-season results of RCTs^1,2 (no statistics provided), RSV-LRTD relative efficacy was the following:

  • - RSVPreF3OA: 83% (season 1) vs 56% (season 2).

  • - RSVpreF: 89% (season 1) vs 79% (season 2).

  • - Actual event rates were not reported.

  • - Hospitalizations or deaths (none due to RSV): 0.008% (RSVPreF3OA) vs 0.04%; 0.006% (RSVpreF) vs 0.02%.

  • - Safety profile: Atrial fibrillation was present in 0.06% to 0.08% of cases versus 0.02% to 0.03% placebo.

    • — Inflammatory neurologic events (eg, Guillain-Barré syndrome): 3 each with RSVPreF3OA (non–placebo-controlled trials) and RSVpreF (placebo=0).

• An RCT (35,541 adults ≥60 years) comparing messenger RNA–1345 vaccine with placebo⁴ found similar results after about 4 months (ie, RSV-LRTD NNV of about 380).

• Limitations: Studies were industry funded and conducted during the COVID-19 pandemic, possibly lowering baseline RSV incidence.

Context

• Risk of RSV (≥50 years): 1.6% to 4.9% per year^5,6 but declined during the COVID-19 pandemic.^6,7

  • - Hospitalization risk (≥60 years): 0.15% per year.⁵

  • - Mortality: 7% to 15% in RSV-hospitalized patients (≥60 years), and increased in those at higher risk.^5,8

• Influenza risk: up to 20 times higher⁷ or similar to RSV.⁹

Implementation

Shared decision making with older adults should weigh risk with preferences and issues like cost (RSVPreF3OA about $250/injection [personal communication with pharmacist Will Chan, Edmonton, Alta; Nov 24, 2023]).¹⁰ It is important to note that patients at high risk (eg, older age, immunocompromised, have comorbidities, reside in long-term care) were minimally (or not) included in RCTs.^1-4 Canadian guidance is forthcoming.