Effectiveness of an Inactivated Quadrivalent Influenza Vaccine in Children and Pregnant Women in Rural Bangladesh: A Phase IV Double-Blind, Cluster-Randomized Trial
In brief
Quadrivalent flu vaccine cut children's influenza B cases by 77% in Bangladesh
In a cluster-randomized trial in rural Bangladesh, the vaccine was 77% effective against confirmed influenza in children during the 2021 B/Victoria wave. Protection was not significant against H1N1 and estimated effectiveness was negative against H3N2; too few cases occurred among pregnant women to assess their protection, and no indirect protection was seen. The findings support child vaccination, but protection varied by strain.
- Journal
- International journal of infectious diseases : IJID : official publication of the International Society for Infectious Diseases (Q1)
- Published
- 26 October 2026
- Study design
- Randomized controlled trial
- Evidence level
- Level 1, High (CEBM 1b)
- Authors
- K Zaman, Warda Haque, Mai Chi Trieu, Amit Bansal, Anders Bonnevie, Sarah Lartey, et al.
- PMID
- 42933529
- DOI
- 10.1016/j.ijid.2026.109209
Why clinicians should know about it
- Picked for Pediatrics and Child Health (paper of the day, 27 October 2026): Randomized trial evaluates influenza vaccine effectiveness in young children
Abstract
OBJECTIVE: Influenza remains a major cause of morbidity and mortality in low- and middle-income countries (LMICs). This Phase IV, double-blind, cluster-randomized trial evaluated the Vaccine Effectiveness (VE) of a quadrivalent inactivated influenza vaccine (QIV) among children under 5 and pregnant women in rural Bangladesh. METHODS: Twenty villages in Matlab, Bangladesh were randomized 1:1 to receive either QIV or inactivated poliovirus vaccine (IPV) as control. Vaccination occurred between April and June 2021, with follow-up surveillance through December 2022. Seventy-five pregnant women (28-34 weeks of gestation) and 2,736 children aged 6-59 months received one dose or two doses at 4-week interval, respectively, of the assigned vaccine. The participants and villagers having influenza-like illnesses (ILI) were monitored and specimens were tested for influenza using real-time Reverse Transcriptase PCR. RESULTS: QIV provided strong protection during the influenza B/Victoria wave (April-August 2021), with adjusted total vaccine effectiveness (VE) of 77.4% (95% CI: 47.4-90.3) in children and 77.9% (95% CI: 48.9-90.5) among all participants. Among pregnant women, only two laboratory-confirmed influenza cases occurred, both in the control group; the small number of events precluded a reliable assessment of vaccine effectiveness in this subgroup. VE was low and non-significant during the influenza A/H1N1 wave, and negative during the influenza A/H3N2 wave. No indirect protection was observed among unvaccinated villagers. CONCLUSIONS: QIV was effective against influenza B/Victoria and reduced ILI cases during the influenza B wave. Findings support including influenza vaccination for children in national programs.
Abstract as published, via PubMed.
For healthcare professionals. The summary is generated by AI from the published abstract, and the evidence level is assigned automatically from the study design on the Oxford CEBM hierarchy. Neither is medical advice. Read the full paper before changing practice.