Maternal RSV vaccine and a small gestational-hypertension signal

Design

Systematic review and meta-analysis (3 randomised trials, 6 retrospective cohorts)

Population

148,267 vaccinated vs unvaccinated or placebo pregnancies

Primary outcome

Hypertensive disorders of pregnancy

Effect

Risk ratio 1.08 (95% CI 1.02 to 1.13); randomised-only risk ratio 1.12 (0.87 to 1.43)

The bivalent RSV prefusion F vaccine (RSVpreF) is offered in pregnancy to protect infants from RSV lower respiratory tract disease. The pivotal phase 3 trial showed a numerical imbalance in hypertensive disorders that did not reach significance, and postmarketing studies have disagreed. This meta-analysis pooled nine studies — three randomised trials and six retrospective cohorts, 148,267 pregnancies.

Overall, vaccination was associated with a small but statistically significant rise in hypertensive disorders, risk ratio 1.08 (95% CI 1.02 to 1.13), driven by the observational studies. The randomised trials alone gave a directionally similar but non-significant estimate, risk ratio 1.12 (0.87 to 1.43). The signal was confined to gestational hypertension, with no significant association for pre-eclampsia or eclampsia.

The practical reading is to keep offering the vaccine. The infant benefit is substantial and the maternal signal is small and uncertain; it belongs in shared decision-making and in routine blood-pressure monitoring, not in withholding the vaccine.

• Meta-analysis of 9 studies (3 randomised trials, 6 cohorts), 148,267 pregnancies.
• Overall hypertensive-disorder risk ratio 1.08 (95% CI 1.02 to 1.13), driven by the observational studies.
• Randomised trials alone: risk ratio 1.12 (0.87 to 1.43), not significant, I-squared 0 percent.
• The signal was confined to gestational hypertension; no significant link with pre-eclampsia or eclampsia.
• Continue to offer RSVpreF in pregnancy and monitor blood pressure; fold the signal into counselling.

Why it matters

A phase 3 numerical imbalance has worried some clinicians; this quantifies the signal and locates it in gestational hypertension, not pre-eclampsia.

Don't overread it

The significant estimate rests on observational studies; the randomised data alone did not reach significance.

The statistics, in plain English

The overall interval sits just above 1.0, so the signal is statistically significant but small; the randomised-only interval crosses 1.0, meaning trial evidence alone cannot confirm it, and residual confounding is possible in the cohorts (I-squared 61 percent).

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