Experts Weigh Flu Vaccine Timing in Pregnancy and Pediatric Uptake

The timing of influenza vaccination during pregnancy may affect how well infants are protected, while pediatric vaccination rates are falling after recent seasons to the lowest in more than a decade, experts said at IDWeek 2026.¹

In a Meet-the-Professor session on October 22, 2026, titled "Influenza Prevention: Rethinking the Paradigm of Vaccinating Children and Pregnant Women," Suchitra Rao, MD, a professor of pediatrics (infectious diseases and hospital medicine) at the University of Colorado School of Medicine and Children's Hospital Colorado, and Samantha M. Olson, MPH, an epidemiologist and lead of influenza work in the New Vaccine Surveillance Network (NVSN) at the CDC's National Center for Immunization and Respiratory Diseases, presented data on pediatric uptake and maternal immunization. The session was moderated by Flor M. Muñoz, MD, MSc, an associate professor of pediatrics at Baylor College of Medicine, and Brian Chow, MD, director of the Beall Positive Care Clinic at Harbor-UCLA Medical Center.

Pediatric Burden Remains High as Coverage Declines

The past 2 seasons were designated high severity for children by the CDC and were among the most severe since the 2009 H1N1 pandemic, Rao said. She reported close to 300 pediatric influenza deaths in the 2024-2025 season and 184 in 2025-2026. In the 2025-2026 season, close to 90% of the children who died were unvaccinated, and about 45% had no underlying medical conditions.

A case cohort analysis in Pediatrics covered 1234 influenza-associated pediatric deaths reported from August 2016 through July 2025.² Of the 1086 deaths with vaccination information, 194 children were fully vaccinated. Vaccine effectiveness against death was 80% (95% CI, 75%-84%) overall, 77% (95% CI, 71%-82%) among children with underlying medical conditions, and 87% (95% CI, 84%-89%) among children without known conditions.

Coverage has moved the other way. Pediatric influenza vaccination peaked at 63.7% in 2019-2020 and fell to 49.4% in 2025-2026, well short of the Healthy People 2030 goal of 70%, according to Rao.¹ Parents decline for reasons that include concerns about safety and adverse effects, doubts that the vaccine works, and a belief that their child is unlikely to get very sick.¹ In national survey data, that last belief was the most commonly reported reason in 2023-2024 (48.2%) and has increased more than other reasons since the COVID-19 pandemic.³

Rao advised against 3 techniques: fear appeals that present the disease without context, debates that trigger defensiveness, and data dumps.⁴ She recommended a presumptive, motivational interviewing approach, such as telling families a vaccine has been reserved for their child, asking permission to explore concerns, and finding common ground.

"A provider recommendation is one of the most important factors in terms of decision to vaccinate," she said, adding that a strong recommendation "can be 30 seconds."¹

Vaccinating Beyond the Primary Care Office

CDC data from 2020-2021 that Rao presented indicate that more than 80% of children aged 6 months to 17 years were vaccinated in a medical setting, while school-based vaccination was minimal. In a cluster randomized trial of 44 schools, vaccination rates were higher in schools with school-located programs than in control schools (54.1% vs 47.4%; P < .001).⁵ A stepped wedge trial across 42 schools found higher odds of vaccination in suburban schools (adjusted OR, 1.36; 95% CI, 1.25-1.49), and a pragmatic randomized trial found 1.5 to 1.6 times the odds of vaccination.^6,7 Children in schools with programs also had a 30.8% lower likelihood of influenza, a figure Rao cited.¹

Pharmacies are an emerging setting. In a claims analysis covering 2010 to 2017, pharmacists administered a small share of pediatric influenza vaccinations (3.2%), but that share grew about 19% annually, and recipients skewed older (mean age, 12.65 years).⁸

At Rao's institution, 42% of undervaccinated children hospitalized with influenza had at least 1 missed opportunity visit, most often to subspecialty clinics, followed by the emergency department (ED) and urgent care.^1,9 The institution's Be Influential program combines multidisciplinary champions, electronic health record tools, and dashboards. Separately, the multicenter INFLUENTIAL trial (NCT05832307) is testing a standardized inpatient vaccination program at 11 sites using an adaptive randomized design, with results expected soon, Rao said.¹

A survey of pediatric ED physicians at 166 EDs, with responses representing 61, found that 44.3% offered at least 1 influenza vaccine per year.¹⁰ Concern about patient throughput was the major barrier, although offering vaccination added only about 3 minutes on average, Rao said.¹ At her institution, a standardized ED program increased the odds of vaccination 15-fold (odds ratio, 15.22; 95% CI, 12.39-18.70), with vaccines administered rising from 272 before the program to 1892, 2141, and 755 in 3 intervention seasons.¹¹ Vaccinated children were more likely than unvaccinated children to be publicly insured (64.3% vs 56.0%) and Hispanic (46.0% vs 34.7%). A perioperative program also raised the odds 15-fold.¹

Infant Protection Varies With Timing of Maternal Vaccination

Current recommendations allow influenza vaccination in any trimester using inactivated or recombinant vaccines, and vaccination in July or August can be considered during the third trimester so infants are protected before they can be vaccinated at 6 months, Olson noted.¹

Using NVSN data from 2016 through the most recent season, Olson reported a test-negative design analysis of maternal vaccination and infant influenza illness. Vaccine effectiveness was 41% and statistically significant when mothers were vaccinated at or after 20 weeks of gestation compared with a nonsignificant 25% before 20 weeks. Effectiveness was 44% for infants aged 0 to 2 months and a nonsignificant 25% for those aged 3 to 5 months. It reached 66% when less than 4 months separated maternal vaccination and infant illness.

Infants whose mothers received only the prior season's vaccine during pregnancy had an effectiveness of negative 1%, which was not statistically significant, in a small sample, vs a statistically significant 42% when the mother received the current season's vaccine. Point estimates declined as the interval between maternal vaccination and infant illness grew, but the lower estimates were not statistically significant.¹ Olson illustrated the interval in a timing schematic.¹²

Modeling Favors an Earlier Campaign

Only 17% to 54% of infants at risk of influenza were in utero when vaccines were administered, a CDC modeling analysis found. Shifting vaccination 8 weeks earlier raised that share from 17% to 38% in 2022-2023.¹³ An earlier cost-effectiveness model found the greatest benefit when pregnant women were vaccinated as soon as possible after the vaccine became available.¹⁴ In most seasons from 2011 to 2020, moving vaccination a month earlier averted more modeled infant hospitalizations than reaching 70% coverage in pregnancy, Olson showed.¹ For mothers, she said, higher coverage would avert more hospitalizations, although an earlier campaign still averted additional illnesses in some seasons.

Olson cautioned against waiting to time vaccination for the infant. "We do not want the pregnant woman to wait to receive a flu vaccine," she said, noting that vaccination also protects the mother from influenza and its complications. Her slide summarized efficacy of 50% to 70% in trials and effectiveness of 44% to 64% in observational studies against laboratory-confirmed influenza in pregnancy and 40% effectiveness against hospitalization.

Next Steps for Clinicians and Researchers

Waning protection is less of a concern with pediatric vaccines, so vaccinating in late August or September is likely fine, Rao said. Muñoz said that with only about 1 in 2 children vaccinated, babies should receive their own vaccine at 6 months, when maternal antibody has waned. Olson noted that influenza activity can continue through February and, at some NVSN sites, into May. She said further research should test earlier-season vaccination, a second dose before delivery, and effectiveness by vaccine type.

"We don't want to give up hope, and we need to reinvigorate all of our efforts to try to promote influenza vaccination," Rao said.

References

1. Influenza prevention: rethinking the paradigm of vaccinating children and pregnant women. Presented at: IDWeek 2026; October 22, 2026.
2. Leonard JS, Reinhart K, Lu PJ, et al. Influenza vaccine effectiveness against pediatric death in the United States: 2016-2025. Pediatrics. 2026;158(2):e2026076453. doi:10.1542/peds.2026-076453
3. Kahn KE, Santibanez TA, Jain A, Zhou T, Black CL. Parental reasons for non-receipt of influenza vaccination among children 6 months-17 years and changes over time, 2015-2024. Vaccine. 2025;61:127415. doi:10.1016/j.vaccine.2025.127415
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5. Szilagyi PG, Schaffer S, Rand CM, et al. School-located influenza vaccinations: a randomized trial. Pediatrics. 2016;138(5):e20161746. doi:10.1542/peds.2016-1746
6. Szilagyi PG, Schaffer S, Rand CM, et al. Impact of elementary school-located influenza vaccinations: a stepped wedge trial across a community. Vaccine. 2018;36(20):2861-2869. doi:10.1016/j.vaccine.2018.03.047
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10. Hart R, Feygin Y, Kluthe T, Quinn KG, Rao S, Baumer-Mouradian SH. Emergency departments: an underutilized resource to address pediatric influenza vaccine coverage. Vaccine. 2023;41(47):7026-7032. doi:10.1016/j.vaccine.2023.10.039
11. Alayari A, Ziniel SI, Hawkins E, Mackenzie J, Rao S. Evaluation of an influenza vaccination program in the pediatric emergency department. J Pediatr. 2025;282:114541. doi:10.1016/j.jpeds.2025.114541
12. Olson SM, Sahni LC, Boom JA, Dawood FS, Muñoz FM, Ellington SR. Timing of influenza vaccination during pregnancy. Am J Obstet Gynecol MFM. 2024;6(8):101427. doi:10.1016/j.ajogmf.2024.101427
13. Morris SE, O'Halloran A, Sundaresan D, et al. Heterogeneity in seasonal influenza vaccination opportunity and disease risk during pregnancy and in infants <6 months. Vaccine. 2025;68:127887. doi:10.1016/j.vaccine.2025.127887
14. Myers ER, Misurski DA, Swamy GK. Influence of timing of seasonal influenza vaccination on effectiveness and cost-effectiveness in pregnancy. Am J Obstet Gynecol. 2011;204(s Suppl 1):S128-S140. doi:10.1016/j.ajog.2011.04.009