Influenza vaccine, use of statins, and muscle pain after vaccination.
Large-Scale Taiwanese Study: Increased Risk of Rhabdomyolysis in Statin Users After Influenza Vaccination
In April 2025, Taiwanese researchers published a large population-based study in EClinicalMedicine investigating a possible interaction between statins and seasonal influenza vaccination. Their aim was to determine whether statin users have an increased risk of developing rhabdomyolysis in the days following a flu shot.
Rhabdomyolysis is a severe form of muscle injury in which muscle cells break down, releasing large amounts of muscle proteins (such as myoglobin) into the bloodstream. This can lead to acute kidney failure and is a known—but rare—side effect of statins.
Until now, only case reports had described patients who developed rhabdomyolysis after receiving an influenza vaccine while using statins, but robust population-level data were lacking.
Study Design
The study by Chen et al. used data from Taiwan’s National Health Insurance Research Database (NHIRD) covering the years 2016–2021.
Key characteristics of the study:
Population
Patients aged ≥50 years
First diagnosis of rhabdomyolysis during the study period
Specific analysis of individuals who had received an influenza vaccination within the year prior to diagnosis
Number of cases
5,602 cases of rhabdomyolysis were included
Exposure
Statin use within 30 days and 60 days before the rhabdomyolysis diagnosis
Timing of influenza vaccination relative to the diagnosis
Method
A case-centered analysis was used:
Within the group of rhabdomyolysis cases, the researchers compared how often statin use overlapped with specific time windows after influenza vaccination versus other time periods.
Risk windows studied:
1–7 days after vaccination
8–14 days after vaccination
Reference periods outside these windows
The primary outcome was the odds ratio (OR) for statin-associated rhabdomyolysis, stratified by the timing of influenza vaccination.
Key Findings
1. Increased risk in the first week after influenza vaccination
Among the 5,602 rhabdomyolysis cases:
1,765 patients had used statins within 30 days before diagnosis
1,838 had used statins within 60 days
74 patients had been vaccinated within 7 days before diagnosis
Of these, 30 had used a statin in the 30-day exposure window
For this group:
OR 1.67 (95% CI 1.04–2.69) for statin-associated rhabdomyolysis when the flu shot had occurred in the preceding 7 days (30-day exposure window)
A similar estimate for the 60-day window: OR 1.79 (95% CI 1.12–2.87)
Interpretation:
Among patients who developed rhabdomyolysis, the proportion attributed to statin use was significantly higher if an influenza vaccination had been administered in the previous week.
2. No increased risk after day 7
Among patients vaccinated 8–14 days before their rhabdomyolysis:
97 individuals total, of whom 24 (30-day window) and 26 (60-day window) had used statins
No increased risk was observed:
OR 0.85 (95% CI 0.53–1.36)
No elevated risk was found outside the 1–14-day window either.
In summary:
The data suggest a temporary increase in risk during the first 7 days after influenza vaccination in statin users, but not thereafter.
Possible Explanations
The authors discuss several hypothetical mechanisms:
Immune activation caused by vaccination may trigger inflammatory responses and cytokine release, potentially increasing susceptibility to statin-induced muscle damage.
Pharmacodynamic interaction:
Statins can independently cause myopathy/rhabdomyolysis.
A temporary “stress response” after vaccination might push vulnerable patients over the threshold.
Vulnerable subgroups (elderly, multimorbid, polypharmacy) are overrepresented in both statin-using populations and those targeted for flu vaccination.
The study does not prove causality; it demonstrates a temporal association only.
Clinical Implications
1. Absolute risk remains very low
Rhabdomyolysis is rare—both as a statin side effect and after vaccination.
This study includes only people who already developed rhabdomyolysis, so it does not provide incidence rates in the general population.
Thus, the relative increase (OR ~1.7–1.8) does not imply a large absolute risk.
2. Increased awareness for healthcare professionals
The authors suggest that clinicians should be more alert to symptoms of rhabdomyolysis in statin users during the first week after vaccination, such as:
Severe muscle pain or weakness
Dark brown/cola-colored urine
Unexplained fatigue or malaise
In such cases, testing CK and renal function, and reassessing statin therapy, may be appropriate (clinical decisions remain the responsibility of the treating physician).
3. No reason to stop statins or flu vaccination routinely
Context is essential:
Influenza vaccination significantly reduces the risk of severe influenza, hospitalization, and mortality in older people and those with comorbidities.
Statins substantially reduce cardiovascular risk in high-risk patients.
Therefore, the authors emphasize that their findings do not justify stopping statins or avoiding flu vaccination. Instead, they recommend:
Careful monitoring of patients with previous statin-associated muscle symptoms
Individual risk–benefit assessment when necessary
Increased vigilance during the first week after vaccination
Limitations of the Study
No incidence data
The study only examined patients with rhabdomyolysis; absolute population risk remains unknown.
Residual confounding
Claims databases cannot fully account for factors such as statin dose, concomitant myotoxic drugs, alcohol use, or extreme exertion.
Generalizability
Data come from Taiwan, whose population characteristics and vaccination strategies may differ from those in Europe or elsewhere.
Association does not equal causation
Even a strong temporal association does not prove that the flu vaccine caused the increased risk.
Conclusion
The Taiwanese study by Chen et al. shows a significant temporal association between:
Recent statin use (within 30–60 days), and
Influenza vaccination within the 7 days preceding the diagnosis of rhabdomyolysis.
During this short window, the likelihood that rhabdomyolysis was attributed to statin use appeared 1.7–1.8 times higherin vaccinated individuals than in other periods.
No increased risk was observed outside the first week.
Practically, this means:
Greater attention to muscle-related symptoms in statin users during the first week after influenza vaccination.
No justification for discontinuing statins or avoiding vaccination; the benefits remain substantial.
Further international and prospective research is needed to better understand this potential vaccine–drug interaction.