Disparities in the Availability and Acceptance of Nirsevimab in Massachusetts

Using electronic health record data from a statewide pediatric primary care network of 79 practices that care for ∼400 000 children in Massachusetts, practice and patient characteristics between October 7, 2023, and November 30, 2023, were analyzed. Eligible infants were active patients ≤8 months of age as of November 30, 2023, with at least 1 office visit. When comparing offices that carried nirsevimab to those that did not, we controlled for practice characteristics (size, urban/suburban location, number of eligible patients, and provider age, sex, and type) and patient characteristics (age in weeks, sex, insurance, race/ethnicity, preferred language, income quartile by ZIP code, and medical complexity). Within practices offering nirsevimab, we compared patients who did and did not receive nirsevimab by November 30, 2023, controlling for all patient characteristics. Race/ethnicity were self-reported and included as they have been shown to be associated with differences in childhood vaccination rates.⁵ Risk ratios (RRs) were calculated using a bivariable log-binomial model, a generalized linear model for a binomial outcome with a log-link function, for each characteristic. Adjusted RRs were calculated using a multivariable log-binomial model. Individual patient characteristic comparisons accounted for patient practice as a fixed effect. All data were analyzed using SAS 9.4 (SAS Institute, Cary, North Carolina). The Boston Children’s Hospital institutional review board approved this study.

Practices offering nirsevimab were larger (compared with small practices, RR, 2.12; 95% confidence interval [CI], 1.15–3.92) for medium practices and 2.12 (1.16–3.90) for large; Table 1), had lower proportions of publicly insured patients (compared with commercially insured; RR, 0.97 [0.95–0.98]), and had lower proportions of patients living in lower income ZIP codes (compared with highest quartile; RR, 0.93 [0.91–0.95], 0.89 [0.87–0.91], 0.86 [0.84–0.88] for second through fourth quartiles, respectively). Within practices administering nirsevimab, 47.3% of eligible patients received it. Factors negatively associated with nirsevimab receipt were older age (RR, 0.98 [0.97–0.99] per 1-week increase; Table 2), public insurance (RR, 0.76 [0.69–0.84]), and living in lower income ZIP codes (compared with highest quartile, RR, 0.90 [0.81–0.99] and 0.82 [0.67–0.99] for third and fourth quartiles, respectively). Factors positively associated with receipt of nirsevimab were non-English as a preferred language (RR, 1.10 [1.01–1.19]) and medical complexity (compared with no chronic disease; RR, 1.14 [1.06–1.23] and 1.24 [1.11–1.38] for noncomplex chronic disease and complex chronic disease, respectively).

Our analysis demonstrates differences in nirsevimab uptake across practices and patients in the early months of availability in Massachusetts. Practices not administering nirsevimab were significantly smaller and served higher proportions of publicly insured patients and those living in less affluent ZIP codes. Notably, even within practices that administered nirsevimab, there were disparities in which patients received it, with publicly insured patients and those living in less affluent ZIP codes significantly less likely to do so.

Our observation that insurance type was strongly associated with nirsevimab receipt is consistent with other data demonstrating that insurance type is a predictor of immunization.^6–8 Greater receipt among more affluent patients may reflect increased awareness and acceptance by their parents, more opportunity to complete an appointment to receive it, and/or bias among administering clinicians in terms of how the immunization is discussed.

Although the restricted availability of nirsevimab in 2023 limited distribution opportunities,⁴ future efforts should be made to correct the potential disparities observed in our analysis. Public health officials and manufacturers could focus on increasing immunization availability to practices caring for publicly insured and economically diverse patients. Additionally, once practices have nirsevimab, outreach to less privileged families and culturally sensitive education about the benefits of immunization could avoid further perpetuating health inequalities and encourage the opportunity for immunization for all eligible infants.

Because this study exclusively examined practices in Massachusetts, findings may not be nationally generalizable. We were unable to confirm whether mothers had received an RSV vaccine; however, only 4.6% of eligible pregnant persons had received the vaccine by November 23, 2023,⁹ making it unlikely that maternal vaccination disqualified a significant number of infants during the study period.

CI

confidence interval

RR

relative risk