#379 Bumpin’ Up the Protection? RSV Vaccine in Pregnancy
CLINICAL QUESTION
How effective and safe is the respiratory syncytial virus (RSV) vaccine (AbrysvoTM) when given during pregnancy?
BOTTOM LINE
The RSV vaccine (AbrysvoTM), approved by Health Canada in pregnancy, reduces severe RSV infections (0.5% infection rate versus 1.8% placebo) and RSV hospitalizations (0.5% versus 1.3%) at 180 days in infants. Preterm births were numerically, but not statistically, higher with this vaccine versus placebo. Administration is limited to 32-36 weeks’ gestation to mitigate this potential risk. Guidelines recommend nirsevimab for infants over prenatal vaccine where indicated.
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EVIDENCE
- Focused on key randomized controlled trials (RCTs) of recombinant stabilized prefusion F protein subunit vaccine (RSVpreF, AbrysvoTM): No systematic reviews of RSVpreF only. Results are for infants and statistically different unless specified. All industry funded.
- Efficacy: RSVpreF versus placebo, given 24-36 weeks gestation (mean: 31 weeks):1,2
- 7392 pregnant women; 7128 infants (94% born 37-42 weeks);1
- Severe RSV infection:
- At 90 days: 0.2% vs 0.9% (placebo), number needed to vaccine (NNV)=143.
- At 180 days: 0.5% versus 1.8% (placebo), NNV=77.
- RSV hospitalization:
- At 90 days: 0.3% vs 0.9% (placebo), NNV=167.
- At 180 days: 0.5% vs 1.3% (placebo), NNV=125.
- Limitations: RCT stopped early; limited RSV cases during study period (COVID-19 pandemic).
- Severe RSV infection:
- 406 pregnant women; 403 infants (mean gestational age: 39 weeks);2
- Severe RSV infection: 0.3% versus 2.9% placebo (no statistics reported).
- Limitations: interim analysis, few events.
- 7392 pregnant women; 7128 infants (94% born 37-42 weeks);1
- Safety:
- Preterm birth: 5.7% versus 4.7% (placebo), no statistical difference.1
- Observational study: 5.9% versus 6.7% (placebo), no statistical difference (administered at 32-36 weeks).3
- Preterm birth: 5.7% versus 4.7% (placebo), no statistical difference.1
CONTEXT
- In Canada, RSV causes:4
- Childhood hospitalizations: ~2,500/year.
- Mortality: 2-3 per 1000 hospitalized.
- Guidelines recommend:5
- Nirsevimab (for infants) preferentially over prenatal RSVpreF vaccine citing greater efficacy and safety data. No direct comparison available.
- RSVpreF administration: 32-36 weeks gestation (due to potential risk of preterm delivery).
- Preterm births: Safety signal with different vaccine (RSVpreF3).
- Administered to 5328 pregnant women at 25-36 weeks gestation.6
- Preterm birth: 6.8% versus 4.9% placebo, NNH=55.
- Systematic review (three RSV vaccines, 4 RCTs): little/no difference in preterm birth.7
- Administered to 5328 pregnant women at 25-36 weeks gestation.6
- Cost:8 $280. Coverage varies by province.
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Where I practice this vaccine is expensive and not covered by provincial medical. Bummer.