Disparities in Nirsevimab Uptake Over 2 Seasons

Nirsevimab, a monoclonal antibody for respiratory syncytial virus (RSV) prophylaxis, debuted during the 2023 to 2024 RSV season. Despite universal recommendation, both incomplete uptake and disparities in nirsevimab receipt exist.1,2 Nirsevimab administration is important because it is highly effective in preventing RSV infection and hospitalization in young infants.3 The objective of this study was to determine if (1) nirsevimab uptake increased within a large pediatric primary care network and (2) if previously identified disparities persisted in its second RSV season.A cohort of infants younger than 8 months from 32 primary care practices across New Jersey and Pennsylvania within the Children’s Hospital of Philadelphia network was generated as previously described.1 Infants with maternal RSV vaccination were excluded. The 2023 to 2024 RSV season was defined as October 1, 2023, through March 31, 2024, and the 2024 to 2025 RSV season as October 1, 2024, through March 31, 2025. We included infants ineligible to receive nirsevimab in the birth hospital due to being born outside of RSV season (April through September) and, therefore, reliant on their primary care practice to receive it, allowing the exploration of factors potentially associated with nirsevimab uptake within the context of the patient’s medical home.Nirsevimab administration and patient age, sex, race and ethnicity, birthweight, insurance status, Childhood Opportunity Index (COI), and visit type were extracted from the electronic health record (EHR).4,5 Race and ethnicity data were self-reported by patients in the EHR. Although race is a social construct, it is included in the analyses because differences in nirsevimab receipt can highlight potential inequities. Vaccine adherence analyses (up to date for Haemophilus influenzae type b, poliovirus, Streptococcus pneumoniae, diphtheria, tetanus, and pertussis by age 9 months) were conducted as previously described.1Descriptive comparisons of uptake across subgroups are presented as unadjusted proportions. Logistic regression was used to determine factors associated with nirsevimab receipt during each season. We fit a pooled logistic regression model including covariates and season-by-covariate interaction terms. Adjusted ORs and 95% CIs were estimated, and interaction terms were used. Inverse probability weighting was used to address missing data.The eligible primary care cohort included 13 897 patients across both seasons (Supplement Figure 1). Comparable with the 2023 to 2024 season, patients in the 2024 to 2025 season were majority male (51.7%), White (53.0%), non-Hispanic/Latino (81.7%), and nonpublicly insured (64.8%) (Table 1). Preterm birth was not included in Figure 1 as prematurity was colinear with low birthweight as described in our previous work. Although nirsevimab uptake increased from 35% in the 2023 to 2024 season to 67% in the 2024 to 2025 season, lower rates of nirsevimab administration to infants with public insurance (OR, 0.58; 95% CI, 0.50–0.67 compared with private insurance), of Black race (OR, 0.67; 95% CI, 0.56–0.82 compared with White infants), and at an older age at start of RSV season (OR, 0.81; 95% CI, 0.79–0.84 for each additional month) persisted into season 2 (Figure 1). Lower COI no longer remained significant (OR, 0.90; 95% CI 0.71–1.14).Overall, 23.5% of children received nirsevimab at nurse (vaccine administration only) visits. Notably, infants of White race (30.9%), with very high COI (32.9%), and with nonpublic insurance (31.1%) had higher unadjusted rates of nirsevimab administration at nurse visits compared with those of Black race (7.1%), with public insurance (8.4%), and with low COI (6.4%). Infants who were fully vaccinated (38.7%–75.5%), partially vaccinated (21.7%–43.3%), and unvaccinated (0.7%–2.4%) against other routine pathogens all increased nirsevimab uptake from the 2023–2024 to 2024–2025 RSV season.Although primary care nirsevimab uptake doubled between the 2023–2024 and 2024–2025 RSV season, the majority of previously identified disparities in RSV administration remained across this large, diverse primary care network. These data suggest that targeted interventions are required to increase protection for all infants at risk of RSV infection.Infants who were publicly insured or Black remained significantly less likely to receive nirsevimab. The reasons for the observed disparities are unclear. Stark differences in rates of nirsevimab administration at nurse visits—encounters scheduled outside of normal well and sick visits and specifically created for vaccine administration—suggest health care access might contribute. Future work could explore interventions to increase nirsevimab uptake by expanding access to nurse visits and encouraging uptake during sick visits for infants with mild illnesses. Additional factors including institutional racism and differences in trust in vaccine safety among sociodemographic strata may also contribute but were not explored in the current study.Unsurprisingly, nirsevimab uptake was highest among those fully vaccinated with routine immunizations, which has been shown with other respiratory vaccines.6 Although all groups increased uptake from the 2023–2024 season to the 2024–2025 season, universally unvaccinated children almost never received nirsevimab.Limitations include the single-center study design, which limits generalizability, and inability to identify reasons for lack of nirsevimab administration, which would help guide quality improvement efforts. Although other studies confirm these disparities, to our knowledge, this is the first to demonstrate that disparities persist across multiple seasons despite increased uptake and demands examination of the drivers of these disparities to inform efforts to increase nirsevimab administration for all eligible infants.7–9