BACKGROUND: Incomplete capture of COVID-19 vaccination in claims data can lead to misclassification of vaccination status in studies using real world data. As COVID-19 vaccine administration may occur without reimbursement from payers, the capture in claims data of vaccine exposure information needed for vaccine safety studies is not currently well understood.
OBJECTIVE: To assess capacity for identifying health insurance plan enrollees with Janssen Ad26.COV2.S COVID-19 vaccination within 4 US health insurance databases in preparation for an observational post-authorization safety study (PASS).
METHODS: Research partners provided A26.COV2.S counts of vaccinees in May 2021, which included demographic characteristics of vaccinees and source of exposure information as recorded in claims. Partners also provided monthly counts from October 2021 through January 2022 and responded to surveys in May 2021 and November 2021. The surveys included information regarding COVID-19 vaccine capture and timeliness in claims data, and potential linkages to states’ Immunization Information Systems (IISs).
RESULTS: In May 2021, we identified 350,532 enrollees with Ad26.COV2.S vaccination in claims data; of these 51% were female, 47% were 18-49 years, 36% were 50-64 years, and 17% were ≥65 years. Vaccine administrations were most commonly recorded in claims with national drug codes (58%) followed by vaccine administration codes (30%); 11% of enrollees had multiple sources of information. The majority of vaccination claims (approximately 77%) were recorded in outpatient settings; 17% had no setting identified, 5% occurred in other settings, and only 1% were captured in mass vaccination settings. Pharmacy claims had the shortest lag time (~1 month) and inpatient claims the longest (~6 months). As of the November 2021 survey, 2 of 4 partners were conducting linkage with IISs in 9 states and negotiating with 14 others. Timing and frequency of IIS linkage varied by partner and IIS, but typically occurred either monthly or weekly. The ability to incorporate IIS records into databases is still being determined. By January 2022, we identified 566,891 enrollees with Ad26.COV2.S vaccination.
CONCLUSIONS: As the extent of missing COVID-19 vaccine information in claims is still unknown, the potential for exposure misclassification should be considered in the design of vaccine safety studies. An active comparator design and a self-controlled risk interval design are planned to be used in this US PASS to overcome potential misclassification of unexposed vaccination status. Ongoing work includes assessment of Ad26.COV2.S vaccine uptake in the insurers’ databases and the ability to incorporate IIS records.
