Currently accepted at: JMIR Public Health and Surveillance
Date Submitted: Jun 2, 2026
Date Accepted: Oct 13, 2026
Date Submitted to PubMed: Oct 14, 2026
This paper has been accepted and is currently in production.
It will appear shortly on 10.2196/103278
The final accepted version (not copyedited yet) is in this tab.
An "ahead-of-print" version has been submitted to Pubmed, see PMID: 42872403
BCG vaccination and first hospitalization in children younger than 5 years: a nationwide cohort study in Portugal
ABSTRACT
Background:
The BCG, used to prevent tuberculosis, has been associated with beneficial non-specific effects (NSEs), including reduced childhood morbidity and mortality. In Portugal, universal neonatal BCG vaccination was discontinued in 2016, creating a natural experiment to evaluate potential NSEs by comparing first hospitalization outcomes between vaccinated and unvaccinated children.
Objective:
To compare the risk of first hospitalization between BCG-vaccinated and unvaccinated children, with secondary analyses examining cause-specific hospitalizations.
Methods:
We conducted a nationwide retrospective cohort study including all children under five born in mainland Portugal between July 1, 2010 and June 30, 2021. Data were obtained from linked national health registries. Follow-up began at day seven of life and continued until first hospitalization, age five, or end of study. BCG vaccination was modeled as a time-dependent exposure in Cox proportional hazards models to estimate hazard ratios for first hospitalization and Kaplan–Meier curves were used to compare cumulative incidence. Models were adjusted for sex, birth year, birth season, comorbidities, and child health surveillance visits. Cause-specific analyses and hospitalization duration (≥3 days) were also examined.
Results:
Among 544,794 children, 66.5% received BCG vaccination. Over 1,781,194 child-years of follow-up, 169,286 first hospitalizations were recorded. After adjustment, BCG vaccination was associated with a higher risk of first hospitalization [(adjusted HR 1.15 (95% CI: 1.13–1.16)]. In cause-specific analyses, BCG vaccination was associated with a modest 8% reduction in first respiratory hospitalizations [(adjusted HR 0.92 (95% CI: 0.89–0.95)]. Most hospitalizations were short, and prolonged admissions were slightly less frequent among vaccinated children.
Conclusions:
BCG vaccination was not associated with a reduced risk of first all-cause hospitalization but was associated with a modest reduction in the risk of first respiratory hospitalization. Clinical Trial: ClinicalTrials.gov (NCT05471167)
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