(C-145) No Claim Left Behind: Viability of Assessing Early Real-World Vaccine Effectiveness in Open and Closed Administrative Healthcare Claims

Background: Adjudicated closed administrative healthcare claims data are commonly used in real-world analyses with a data lag, whereas using open claims data may support real-time (RT) analyses to allow for earlier estimates of vaccine effectiveness (VE).

Objectives: Assess vaccine effectiveness (VE) of the mRNA-1273.815 vaccine against hospitalization with COVID-19 in RT using open and closed claims in relation to a closed claims analysis.

Methods: Using HealthVerity claims, US adults ≥18 years, vaccinated with mRNA-1273.815 (12 September 2023-31 December 2023) were matched on calendar date, demographics, bivalent vaccine receipt, and prior medical claims frequency, to individuals who did not receive mRNA-1273.815. Cox models estimated hazard ratios and VE (1-HR*100) among inverse probability weighted cohorts. RT analyses used a datacut available 2 February 2024, while closed claims analyses used a datacut available 30 April 2024. Both analyses had identical study and follow-up periods through 26 January 2024.

Results: In RT and closed claims analyses, 1,134,585 and 1,272,161 individuals were identified that received mRNA-1273.815. Demographic and comorbidity profiles were similar; weighted baseline characteristics were balanced.

In RT, incidence rate was 87.0 (95% CI 75.1-100.3) and 196.6 (177.4-217.2) per 100,000 person-years (PY), among exposed and unexposed patients, respectively; weighted VE was 54% (95% CI 46%-62%). In closed claims analysis, incidence rate was 516.5 (490.7-543.3) and 1,050.0 (1,009.9-1,091.3) per 100,000 PY, among exposed and unexposed, weighted VE was 51% (95% CI 48%-54%).

Conclusions: Real-time analysis of open and closed claims resulted in substantially lower rates of COVID-19 hospitalizations compared with the closed claims analysis, indicating a sizable proportion of outcome claims were not available. Nevertheless, outcome distribution between the vaccinated and unvaccinated groups was similar, resulting in similar VE. Findings suggest a real-time analysis could be appropriate for early evaluation of VE, but additional data are needed.