# Interaction between influenza vaccine and statins affecting the risk of rhabdomyolysis in Taiwan: a nationwide case-centred analysis

## TL;DR

This study finds that recent influenza vaccination may increase the risk of rhabdomyolysis in people taking statins, especially within 7 days of vaccination.

## Contribution

The study provides population-level evidence of a potential interaction between influenza vaccination and statin use in causing rhabdomyolysis.

## Key findings

- Patients on statins who were vaccinated within 7 days had a 67% higher risk of rhabdomyolysis.
- The increased risk was not observed when vaccination occurred 8–14 days before diagnosis.
- The association was significant within 30 and 60-day statin use windows post-vaccination.

## Abstract

Literature suggests a potential interaction between influenza vaccination, statin use and rhabdomyolysis, but evidence is limited to case reports.

Using out- and inpatient health records from Taiwan’s National Health Insurance Research Database (NHIRD) between January 2016 and December 2021, we retrospectively constructed a nationwide cohort of patients aged 50 years and older, first-ever diagnosed with rhabdomyolysis, focusing on those who received an influenza vaccine within the preceding one year. We applied a case-centred analysis to evaluate the interaction between statin use and influenza vaccination within specific risk intervals: 1–7 days and 8–14 days post-vaccination, as well as 30-day and 60-day windows for statin use prior to rhabdomyolysis diagnosis. The main outcome measures were odds ratios (ORs) for statin-associated rhabdomyolysis, stratified by timing of influenza vaccination.

Among the 5,602 rhabdomyolysis cases analysed, 1,765 patients were exposed to statins within 30 days, and 1,838 patients were exposed within 60 days. 74 individuals were vaccinated within 7 days prior to their diagnosis, 30 of which were taking statins inside the 30-day interval, these individuals were found to be at a significantly higher risk of statin-related rhabdomyolysis (OR: 1.67, 95% confidence interval: 1.04–2.69). A similar risk was observed when the statin risk interval was extended to 60 days, 74 vaccinated rhabdomyolysis patients with 32 within the 60 day window (OR: 1.79, 95% confidence interval: 1.12–2.87). However, this increased risk was not observed among the 97 individuals (24 patients in the 30 day window and 26 in the 60 day) who received vaccination 8–14 days before rhabdomyolysis onset (OR: 0.85, 95% confidence interval: 0.53–1.36), and not in those vaccinated outside these risk intervals.

Our results suggest a significant temporal association between recent influenza vaccination and increased risk of statin-associated rhabdomyolysis within 7 days post-vaccination. These findings highlight the need for healthcare providers to monitor for rhabdomyolysis symptoms following influenza vaccination in patients receiving statin therapy. Further confirmation in larger prospective international studies is warranted to better understand this potential association.

National Science and Technology Council of Taiwan (NSTC 112-2628-B-006-003-; NSTC 113-2628-B-006-009-) and the 10.13039/501100004737National Health Research Institutes of Taiwan (NHRI-11A1-CG-CO-04-2225-1; NHRI-12A1-CG-CO-04-2225-1; NHRI-13A1-CG-CO-04-2225-1; NHRI-14A1-CG-CO-04-2225-1).