Maternal vaccination lowers infant severe infections
Vaccination during pregnancy was linked to fewer infant hospital and emergency department visits for influenza and pertussis.
*Population-based matched cohort study; Level 2b (OCEBM).

Citation

Morabito G, Corrao G, Giaquinto C, Cantarutti A, Di Chiara C. Maternal Vaccine Receipt and Infant Hospital and Emergency Visits for Influenza and Pertussis. JAMA Network Open. 2026;9(1):e2553179. doi:10.1001/jamanetworkopen.2025.53179

Background

Infants under 6 months have limited direct vaccine options for influenza and early pertussis prevention. Maternal vaccination may protect infants, but evidence for severe outcomes (hospital and emergency visits) has been limited in Italy.

Patients

Live-born mother–infant pairs in Lombardy, Italy (2018–2022). Exclusions included incomplete public health coverage around pregnancy, inability to link mother and infant records, and missing key demographic data. For influenza analyses, only deliveries from September through February were included.

Intervention

Influenza vaccine during pregnancy; and tetanus, diphtheria, and acellular pertussis vaccine during pregnancy.

Control

Matched unvaccinated pregnant individuals (matched on delivery month/year, gestational age at birth, and singleton vs multiple pregnancy).

Outcome

Infant hospitalization or emergency department visit diagnosed as influenza or pertussis (composite for each infection).

Follow-up Period

Birth to 6 months (pertussis follow-up also censored at infant pertussis vaccination when recorded).

Results

Vaccine coverage among eligible pregnancies was 6.4% for influenza and 41.0% for the pertussis-containing vaccine.
Maternal vaccine during pregnancy Infant outcome Adjusted hazard ratio (95% CI) Estimated vaccine effectiveness
Influenza vaccine Influenza-related hospitalization or emergency visit (primary) 0.30 (0.10 to 0.91) 69.7% (8.7% to 90.0%)
Pertussis-containing vaccine Pertussis-related hospitalization or emergency visit (primary) 0.11 (0.02 to 0.88) 88.6% (11.5% to 98.5%)

Limitations

Observational design leaves room for unmeasured differences (for example, health-seeking behavior). Diagnoses from administrative records may be misclassified. Few events limited subgroup analyses (such as timing by trimester). Private vaccinations and care outside the public system may be missed.

Funding

Italian National Recovery and Resilience Plan (PRIN2022; CARICE project); no funder role.

Clinical Application

Reinforces recommending influenza and pertussis vaccination during pregnancy to protect infants under 6 months; prioritize outreach to improve low influenza vaccine uptake.