(SLC-049) Risk of Atrial Fibrillation After Bivalent COVID-19 Vaccination During the 2022-2023 Season

Background: Past studies have evaluated the risk of ischemic stroke, but not atrial fibrillation (AF), following bivalent COVID-19 vaccination. AF is a risk factor for ischemic stroke, and AF was reported to US and European pharmacovigilance systems as an adverse event following mRNA COVID-19 vaccination.

Objective: Our study objective was to examine the risk of AF after bivalent COVID-19 vaccination during the 2022-2023 season.

Methods: Using electronic health care records, we conducted a modified self-controlled case series (SCCS) analysis among eligible members aged ≥18 years from Kaiser Permanente Southern California, a large integrated health care system in the US. We required membership on September 1, 2022, and followed individuals until March 31, 2023, disenrollment, or death, whichever came first. We included individuals who had a first diagnosis of AF during the study period (defined as ≥1 emergency department or inpatient encounter or ≥2 encounters within a year apart with ICD-10 code I48.0, I48.1, I48.2, or I48.91), without diagnosis of AF from October 1, 2015 to August 31, 2022. In the SCCS analyses, risk intervals were specified as 1-21 days and 1-42 days after receipt of bivalent COVID-19 vaccines (Pfizer-BioNTech and Moderna), with person-time outside these risk intervals serving as control intervals. Day 0 events on the day of vaccination were excluded. Because individuals who had AF events might postpone or avoid vaccination, we used a modified SCCS approach for event-dependent exposures to estimate relative incidence (RI), comparing incidence of AF in the risk interval and control interval, by maximizing a Poisson pseudolikelihood. AF events occurring among eligible individuals who did not receive bivalent COVID-19 vaccines were included to account for seasonality. We conducted overall and subgroup analyses by age ( <65 years, ≥65 years).

Results: There were 5,930 AF events during the study period, with 1,360 among Pfizer-BioNTech bivalent recipients, 1,162 among Moderna bivalent recipients, and 3,408 among non-recipients. For Pfizer-BioNTech bivalent vaccine, the RI of AF was 0.87 (95% CI: 0.71, 1.07) during the 21-day risk interval and 0.88 (0.75, 1.03) during the 42-day risk interval. For Moderna bivalent vaccine, the RI of AF was 0.95 (0.76, 1.17) during the 21-day risk interval and 0.91 (0.77, 1.08) during the 42-day risk interval. Point estimates for RI by age group ranged from 0.59 to 1.04, with 95% CIs including 1.

Conclusions: Using a modified SCCS design, we did not observe an increased risk of AF in the 21 or 42 days following bivalent COVID-19 vaccination. Future research could explore potential effect modification by co-administration of influenza vaccine and prior SARS-CoV-2 infection.