Context and Objective

Health inequalities in early childhood (HIEC) contribute significantly to avoidable morbidity and mortality in high-income countries.

Respiratory syncytial virus infection is a cause of early childhood morbidity and mortality, and until the approval of nirsevimab in 2022, no universal prevention programs existed. The first immunization campaign with nirsevimab began in France in September 2023, with a free single dose recommended for infants born after February 6, 2023.

This study explored potential sociodemographic inequalities associated with nirsevimab uptake during this campaign.

Methods

Using the French National Health Data System, this cohort study included all infants eligible for nirsevimab born February 6 to September 15, 2023. The event of interest was outpatient administration of a single-dose nirsevimab immunization from September 15, 2023, to January 31, 2024. However, because of national shortages during this initial campaign, only a fraction of eligible children received passive immunization.

We compared characteristics of immunized and unimmunized infants, including general characteristics (sex, gestational age, birth weight and period, and social security affiliation type), individual socioeconomic indicators (type of birth hospital, complementary solidarity health insurance status, and consultations in maternal and child welfare centers), and indicators of sociogeographical inequities (region of residence, residential municipality–related indicators of deprivation [French Deprivation Index], and health care accessibility [General Practitioners’ Localized Potential Accessibility]).

Results

Of 328 131 infants in the study, 42 082 infants (12.8%) received nirsevimab (mean [SD] age at administration, 4.8 [2.3] months). Infants who were male (aOR vs female, 1.07 [95% CI, 1.05-1.10]) and born very preterm (aOR vs full term, 2.07 [95% CI, 1.82-2.37]), and in June or July (aOR vs February or March, 1.69 [95% CI, 1.64-1.74]) were more likely to be immunized.

Socioeconomic indicators were associated with nirsevimab immunization. On an individual level, infants whose parents had complementary solidarity health insurance (aOR, 0.38 [95% CI, 0.37-0.39]), were covered by the agricultural social security scheme (aOR vs the general scheme, 0.86 [95% CI, 0.79-0.93]), and received consultation in maternal and child welfare centers (aOR, 0.78 [95% CI, 0.75-0.82]) and infants born in public hospitals (aOR, 0.81 [95% CI, 0.79-0.83]), living in the most deprived municipalities (quartile 5 [Q5] vs Q1: aOR, 0.41 [95% CI, 0.39-0.42]), or with lower accessibility to general practitioners (Q1 vs Q5: aOR, 0.60 [95% CI, 0.57-0.62]) had significantly lower odds of immunization. We observed regional disparities, with higher immunization coverage in northern France.

Conclusion

This cohort study found significant socioeconomic and geographical disparities in nirsevimab immunization rates during France’s first free outpatient immunization campaign. Infants born in June or July 2023 showed higher immunization rates, likely due to timely recommendations and increased parental awareness of their risk. Disparities occurred among socioeconomically deprived infants and those residing in areas with limited health care access. Geographic disparities may have been exacerbated by supply shortages, disproportionately impacting regions with higher deprivation.