Evening edition · Monday, 2 November 2026
75.5% for the babies, and a 14-day rule for the calendar
A review of real-world studies finds the RSV jab in pregnancy cut infant hospital admissions by three-quarters. The most useful number in it is a date, not a percentage.
Trials told us the RSV vaccine given in pregnancy works. The harder question is whether it works in ordinary clinics, with ordinary timing and ordinary paperwork. A new review of real-world studies, presented at the IDWeek 2026 meeting and reported today, gives a calm answer: yes, if you are not late1.
The review pooled seven studies from Argentina, the UK and the US, covering 3,029 vaccinated mother-and-baby pairs1. When mothers were vaccinated at least 14 days before birth, the vaccine was 75.5% effective against hospital admission for RSV in the baby’s first six months, compared with unvaccinated controls1. Protection was highest in babies aged three months or younger, at 80.8%, and 72.4% across the first six months1. It is a “living” review: the estimates are updated as new studies come out1.
Then comes the number that matters for the calendar. When the jab was given less than 14 days before birth, effectiveness fell to 28%1. That figure comes from a single study, as the lead author, Ariel Bardach of the Institute for Clinical Effectiveness and Health Policy in Buenos Aires, points out, but it fits the biology: a mother needs time to make antibodies and pass them on1. An outside expert, Natasha Halasa of Vanderbilt University Medical Center, said clinicians “should not wait until the end of the eligible window to offer it”1.
The limits are stated too. The studies are observational, they measured hospital admissions rather than intensive care, and they say little yet about premature babies or low-income countries, where the RSV burden is greatest1. The study was funded by Pfizer, which makes the vaccine, and several co-authors are Pfizer employees1. Families also have a second option, antibody injections for the baby, and should be told about both1.
If you are pregnant, or about to be a grandparent, the practical point is small and dull. Ask about the jab at the antenatal appointment, not at the last one. Two weeks is the difference between most of the protection and little of it.
What to watch
- Further updates to the living review as new studies are published; its authors say the estimates are refreshed as data arrive1.
Protection, like post, needs to be sent in time to arrive.
Sources
- Real-World Data Support Maternal RSV Vaccination — Medscape, 02 Nov 2026.
Every figure in this piece traces to a source above or to the desk’s own arithmetic on those sources, marked as such. Quotations are short and attributed. Spot an error? Write to the desk; corrections are logged on the method page.
Commentary for information only. Not investment, legal, tax, medical or political advice. Not an offer or solicitation. Analysis may be incomplete or wrong. Charts show published public data, not a trading feed; binding numbers live with the institutions that publish them.