Summary characteristics of the included studies

Study designSample sizeVaccine receivedAge at inclusionFollow-upKey findingsAnalysis method
Madhi et al. [13]
 Multi-country RCT in 87 sites and 11 countries#4636 women underwent randomisation
Vaccine: n=3045, trial completed in 2907
Placebo: n=1581, trial completed in 1510
Infant group: vaccine n=3008, male n=1556; placebo n=1561, male n=799
RSV F protein nanoparticle vaccine in intervention, or placeboHealthy women aged 18–40 years were enrolled at 28–36 weeks of gestational age180 days and 364 daysVaccine efficacy in infants against RSV-associated LRTI: per-protocol analysis 39.4%; intention-to-treat analysis 32.2%
Vaccine efficacy in infants against RSV-associated LRTI with severe hypoxaemia: per-protocol analysis 48.3%; intention-to-treat analysis 44.4%
Vaccine efficacy in infants against RSV-associated LRTI and hospitalisation: per-protocol analysis 44.4%; intention-to-treat analysis 48.1%
Per-protocol and intention-to-treat analysis
Omer et al. [14]
 Pooled analysis from three RCTs conducted in Nepal (2011–2014), Mali (2011–2014) and South Africa (2011–2013)Maternal group: n=10 002 (vaccine n=5017, control n=4985)
Nepal: n=3693 (vaccine n=1847, control n=1846)
Mali: n=4193 (vaccine n=2108, control n=2085)
South Africa: n=2116 (vaccine n=1062, control n=1054)
Trivalent IIV+ in intervention, or placebo (placebo was normal saline in Nepal and South Africa, meningococcal conjugate vaccine in Mali)Pregnant women with gestational age 17–34 weeks in Nepal, ≥28 weeks in Mali and 20–36 weeks in South Africa6 months in Nepal and Mali, 24 weeks in South AfricaVaccine efficacy in women:
50% against PCR-confirmed influenza
42% during pregnancy; 60% postpartum
Vaccination <29 weeks, efficacy 30%; >29 weeks, efficacy 71%§
H1N1, efficacy 65%; H3N2, efficacy 40%; influenza B, efficacy 63%
Data were pooled and analysed using a one­stage meta-analysis; Poisson regression models were used
Infant group: n=9800 (vaccinated mothers n=4910, control mothers n=4890)NANANAPooled efficacy of maternal vaccination:
First 2 months 56%; 2–4 months 39%; 4–6 months 19%
Vaccination <29 weeks, efficacy 34%; >29 weeks, efficacy 35%
H1N1, efficacy 46%; H3N2, efficacy 45%; influenza B, efficacy 13%

RCT: randomised controlled trial; RSV: respiratory syncytial virus; F: fusion; LRTI: lower respiratory tract infection; IIV: inactivated influenza vaccine; NA: not applicable. #: study conducted in Argentina, Australia, Bangladesh, Chile, Mexico, New Zealand, the Philippines, South Africa, Spain, the UK and the USA. : numbers do not sum because every assigned mother had a liveborn infant, and some had twins. +: VAXIGRIP (SanofiPasteur), sourced from Mumbai (India) in Nepal, and from Lyon (France) in Mali and South Africa. §: no overall association reported between maternal vaccination and low birthweight, stillbirth, preterm birth, and gestational age; at 6 months of infant age, the intervention and placebo were similar in terms of being underweight (weight-for-age), stunted (length-for-age) and wasted (weight-for-length).