Maternal hybrid immunity and risk of infant COVID-19 hospitalizations: national case-control study in Israel.

Publication date: Apr 02, 2024

Hybrid immunity, acquired through vaccination followed or preceded by a COVID-19 infection, elicits robust antibody augmentation. We hypothesize that maternal hybrid immunity will provide greater infant protection than other forms of COVID-19 immunity in the first 6 months of life. We conducted a case-control study in Israel, enrolling 661 infants up to 6 months of age, hospitalized with COVID-19 (cases) and 59,460 age-matched non-hospitalized infants (controls) between August 24, 2021, and March 15, 2022. Infants were grouped by maternal immunity status at delivery: NacEFve (never vaccinated or tested positive, reference group), Hybrid-immunity (vaccinated and tested positive), Natural-immunity (tested positive before or during the study period), Full-vaccination (two-shot regimen plus 1 booster), and Partial-vaccination (less than full three shot regimen). Applying Cox proportional hazards models to estimate the hazard ratios, which was then converted to percent vaccine effectiveness, and using the NacEFve group as the reference, maternal hybrid-immunity provided the highest protection (84% [95% CI 75-90]), followed by full-vaccination (66% [95% CI 56-74]), natural-immunity (56% [95% CI 39-68]), and partial-vaccination (29% [95% CI 15-41]). Maternal hybrid-immunity was associated with a reduced risk of infant hospitalization for Covid-19, as compared to natural-immunity, regardless of exposure timing or sequence. These findings emphasize the benefits of vaccinating previously infected individuals during pregnancy to reduce COVID-19 hospitalizations in early infancy.

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Concepts Keywords
August Case
Israel Control
Vaccinated Covid


Type Source Name
disease MESH COVID-19
disease VO vaccination
disease MESH infection
disease VO vaccinated
disease VO vaccine effectiveness
disease MESH respiratory failure
disease VO effectiveness
disease VO immunization
drug DRUGBANK Coenzyme M
disease MESH pertussis
pathway KEGG Pertussis
disease MESH influenza
disease VO vaccine
disease VO vaccine dose
disease VO vaccination dose
disease VO population
disease VO unimmunized
disease MESH clinical significance
disease VO pregnant women
disease VO frequency
disease VO ANOVA

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