Timing and frequency of antenatal care visits in relation to maternal respiratory syncytial virus vaccine opportunities in four Latin American countries

Jessica A Fleming; Valentina Colistro; Sophia Knudson; Mercedes Colomar

doi:10.1016/j.vaccine.2026.128854

Timing and frequency of antenatal care visits in relation to maternal respiratory syncytial virus vaccine opportunities in four Latin American countries

Vaccine. 2026 Jun 19:88:128854. doi: 10.1016/j.vaccine.2026.128854. Online ahead of print.

Authors

Jessica A Fleming¹, Valentina Colistro², Sophia Knudson³, Mercedes Colomar⁴

Affiliations

¹ Center for Vaccine Innovation and Access, PATH, 437 N 34th St, Seattle, WA 98103, United States. Electronic address: jfleming@path.org.
² Faculty of Medicine, University of the Republic of Uruguay, Avenida General Flores 2125, 11800 Montevideo, Uruguay. Electronic address: Vcolistro@unicem-web.org.
³ Center for Vaccine Innovation and Access, PATH, 437 N 34th St, Seattle, WA 98103, United States. Electronic address: sknudson@path.org.
⁴ Women's, Maternal, Neonatal and Reproductive Health, Health Systems and Services, Panamerican Health Organization, 525 23(rd) St NW, Washington, DC 20037, United States. Electronic address: colomarmer@paho.org.

PMID: 42320380
DOI: 10.1016/j.vaccine.2026.128854

Abstract

Introduction: The Latin American and Caribbean region (LAC) has historically been an early adopter of new vaccines, including the recently introduced maternal vaccine to protect infants against respiratory syncytial virus (RSV). Since maternal RSV vaccination requires gestational age (GA)-specific administration, antenatal care (ANC)-based delivery feasibility depends on ANC visit timing and frequency. We assessed ANC attendance relative to recommended vaccination windows in four LAC countries to inform planning for maternal RSV vaccine implementation and future maternal immunization programs.

Methods: We conducted a retrospective, cross-sectional analysis from Perinatal Information System data across eight tertiary facilities in Bolivia, Ecuador, Honduras, and Uruguay. Women 15-45 years old with ≥1 ANC visit in 2023 and a live, singleton birth at a study facility were included. GA per visit was extracted or derived from last menstrual period or birth data. We defined RSV vaccination eligibility according to Pan American Health Organization (PAHO) (32-36 weeks) and World Health Organization (WHO) (≥ 28 weeks) recommendations. Descriptive analyses summarized ANC initiation, visit timing, and the proportion of women attending visits within eligibility windows.

Results: We included 37,604 women. The median GA at ANC initiation was 12 weeks, ranging from 10 weeks (Uruguay) to 15 weeks (Ecuador). Overall, 63.5% of women attended at least one ANC visit during the PAHO window, with country-specific proportions from 53.6% (Honduras) to 82.3% (Uruguay). Attendance within the WHO window was higher (91.4%). Median ANC attendance was five visits, ranging from five (Honduras) to eight (Uruguay). Earlier ANC initiation was associated with higher visit counts.

Discussion: There is substantial potential for achieving high maternal RSV vaccine coverage in LAC, particularly per broader WHO vaccine recommendations. Where ANC begins later or visits are fewer, narrower vaccine-eligible windows may limit achievable coverage. Strengthening early ANC engagement and immunization counseling may increase vaccination opportunities.

Keywords: Antenatal care; Antenatal care timing; Generic study protocol; Low- and middle-income countries; Maternal immunization; Maternal vaccine; Respiratory syncytial virus; Vaccine implementation.