(341) Early use of Moderna’s mRNA-1273.815 monovalent vaccine: a descriptive analysis of a US Claims database

Background: Although COVID-19 continues to be a leading cause of hospitalizations attributable to respiratory infection and 2023-2024 XBB.1.5 updated vaccines were recommended by the CDC for all individuals >6 months in mid-September 2023, COVID-19 vaccination rates remain low. Data from the US CDC’s National Immunization Survey show that as of 27 January 2024, 22% of the adult population ≥18 years and 41% of the elderly have been vaccinated with a 2023-24 updated COVID-19 vaccine.

Objectives: In this descriptive analysis and in preparation for a vaccine effectiveness study using a target trial emulation approach, we aimed to characterize the population of adults who received mRNA-1273.815 (Moderna monovalent XBB.1.5 updated vaccine) from 12 September 2023 to 26 January 2024.

Methods: This retrospective observational study used HealthVerity open and closed US healthcare claims data (commercial, Medicare Advantage, and Medicaid plans). Adults ≥18 years, who were vaccinated with mRNA-1273.815 vaccination during the study period and had a minimum of 365 days of continuous medical and pharmacy plan claims enrollment prior to the vaccination date (index date) were included. Demographic characteristics were assessed at the index date and underlying medical conditions were assessed based on claims data during the year prior to the index date.

Results: 1,378,717 adults who received the mRNA-1273.815 were included in our analyses of whom 56% were female. The average age was 55.5 years, and 27% were ≥65 years of age. The majority were vaccinated between September and November (17% in September, 52% in October, and 21% in November), and vaccinated individuals were evenly distributed across all regions of the US. 60% of the vaccinated population had at least one underlying medical condition associated with severe COVID-19 outcomes. The most common comorbidities were obesity (22%), mood disorders (19%), and type 2 diabetes (18%). 12% of the vaccinated individuals were immunocompromised.

Conclusions: These initial results indicate that vaccine administration peaked in October 2023 and tapered off into January. Utilization of the vaccine was seen across the population across age groups and among individuals with and without underlying medical conditions. Findings from this early analysis may contribute to a better understanding of vaccination patterns among US adult populations and will be critical in establishing a matched cohort of unvaccinated individuals who will serve as controls in vaccine effectiveness analysis.