Unmasking the Enigma: Influenza Vaccine and the Rare Case of Post-Vaccination Pericarditis

Acute pericarditis is an inflammatory condition involving the pericardium, the double-layered sac that surrounds the heart. It is characterized by chest pain, typically pleuritic and sharp, along with other clinical and laboratory findings indicative of pericardial inflammation. While acute pericarditis following influenza vaccination is rare, it has been reported in medical literature. The relationship between vaccinations, including the influenza vaccine, and pericarditis is particularly interesting, as it has implications for public health and vaccination programs. Understanding the pathophysiological mechanisms behind vaccine-induced pericarditis and recognizing the clinical presentation are essential for healthcare professionals to diagnose, manage, and educate patients appropriately.


Introduction
Infuenza, an annually recurring global health concern, is a contagious respiratory infection caused by the infuenza virus.To combat its widespread impact, routine infuenza vaccination has proven to be an efective preventive measure.It is crucial, however, to acknowledge that, like all medical interventions, infuenza vaccination is associated with potential side efects.One relatively rare side efect of infuenza vaccination is pericarditis [1], an infammatory condition of the pericardium of the heart.Te incidence of hospital admissions of pericarditis is approximately 3.32 cases per 100,000 person-years [2].Tis highlights the low incidence of the disease, despite the estimated incidence being considerably higher at 27.7 cases per 100,000 subjects per year [2,3].Te incidence of pericarditis following infuenza vaccination has not been reported in the existing literature.It is plausible that due to the low incidence of the disease, several cases of post-vaccination pericarditis are underreported [2,3].Tis case report describes a 91-year-old female who exhibited typical symptoms of acute pericarditis three days after receiving an infuenza vaccine.

Case Presentation
We present a case of a 91-year-old female with a past medical history of hypertension, hyperlipidemia, and presbycusis who presented to the emergency department complaining of chest pain, with sudden onset 2 hours prior to presentation.She described the chest pain as central, radiating to the left side of the chest, back, and left shoulder, and worse with inspiration.Te patient also reported a low-grade fever, fatigue, and malaise.Notably, the patient received an inactivated infuenza vaccine two days before the onset of symptoms.She denied any signifcant cardiac history, which was corroborated by her primary provider.On presentation to the ED, she was hypertensive with a blood pressure of (186/94 mmHg), tachycardic with a heart rate of 101 beats per minute (BPM), febrile (T max 100.8 F), and saturating 99% on ambient room air.Upon examination, a pericardial friction rub was noted on auscultation.Laboratory values on admission were signifcant for leukocytosis with a white blood cell count (WBC) of 13.4 k K/uL, erythrocyte sedimentation rate (ESR) of 54 mm/hr, and C-reactive protein (CRP) of 227.9 mg/L.D-dimer and serial troponin markers were negative upon admission (Table 1).Te initial electrocardiogram (ECG) showed no ischemic changes (Figure 1).Subsequent ECG performed 14 hours after the initial ECG showed ST elevations in inferior leads with PR depressions (Figure 2).Computed tomography angiography with intravenous contrast of the chest and aorta showed no evidence of intramural hematoma or dissection with atherosclerotic disease at the origins of the celiac axis, superior mesenteric, and renal arteries.A trace pericardial efusion was also present (Figure 3).A subsequent transthoracic echocardiogram was performed, which did not demonstrate any evidence of pericardial efusion.Te patient's clinical presentation, including chest pain, fever, and the temporal association of these symptoms with the infuenza vaccine, led to a preliminary diagnosis of acute pericarditis.Te patient was admitted for observation and received ibuprofen and colchicine to relieve pain and reduce infammation.Te patient was advised to refrain from strenuous physical activity and was closely monitored for any worsening of symptoms.Her chest pain resolved over the next several days, and the fever subsided.

Discussion
Pericarditis is the infammation of the pericardium, which is a sac-like cavity that encases the heart; however, etiology is not established in 90% of pericarditis cases [3,4].Tis may be due to an infectious or noninfectious cause.Te diagnosis is largely clinical by presentation.It is more likely that males are hospitalized for acute pericarditis [5].Risk factors indicating poor prognosis include temperature >100.4 0 F at presentation, subacute course, presence of tamponade, and resistance to NSAID treatment [6].Tese symptoms may recur, which has been observed within 18 months of initial presentation in 30% of patients [7].Routine laboratory values may reveal an elevated WBC count, ESR and CRP, which are nonspecifc markers highlighting infammation or infection in the body [8].Additionally, cardiac enzymes such as troponins may be elevated [8,9].Colchicine is one drug that is efective in preventing both primary and recurrent pericarditis [9].Te use of colchicine along with NSAIDs has been shown to signifcantly reduce recurrences of this disease in patients with multiple recurrences [10].
Our case illustrates the occurrence of acute pericarditis following infuenza vaccination in an elderly patient, underscoring the importance of vigilance in monitoring post-vaccination symptoms.While vaccine-induced pericarditis is rare, early recognition and appropriate management are essential to prevent complications and optimize patient outcomes.
Upon literature review, Mei et al. highlight a case report which serves as a crucial reminder of the potential rare adverse efects associated with infuenza vaccination.Tey document an 87-year-old patient developing pericarditis post-infuenza vaccination.Tis particular patient did not exhibit ECG abnormalities or elevated troponin levels, which makes this case even more noteworthy, as it challenges the conventional diagnostic markers of pericarditis [1].
Mei and colleagues' case is not an isolated incident, as they also highlight seven other patients with either a possible or well-defned association between infuenza vaccination and pericarditis.Tis collective body of evidence underscores the need for clinicians and healthcare providers to remain alert to the potential link between pericarditis and infuenza vaccination [1].
Moreover, an extensive review of the existing literature reveals a consistent trend in the rapid onset of pericarditis within a week of infuenza vaccination.Notably, Meester, Luwaert, and Chaudron present two cases in which patients developed benign pericarditis within this timeframe [11].In a diferent case, a 40-year-old male is found to have the onset of acute benign pericarditis within fve days of the infuenza vaccination [12].Te temporal correlation between vaccination and the onset of pericarditis observed in these cases suggests a causal relationship.Additionally, there has been one reported case of acute hemorrhagic pericarditis, which required surgical pericardiectomy followed by colchicine treatment [13].
Intriguingly, Streifer et al. present an even more unique case in which a patient experienced pericarditis after receiving the vaccine on two distinct occasions.Tis recurrence strongly implies a cause-and-efect relationship between the infuenza vaccine and pericarditis [14].Although such cases remain rare, they emphasize the importance of recognizing and managing vaccine-induced pericarditis early to prevent complications and optimize patient outcomes.It is not necessary for acute symptomatic pericarditis to be the standalone presentation after vaccination.Tis may coexist along with the exacerbation of Guillain-Barrè syndrome or nephrotic syndrome [15].Kao et al. illustrate two cases and discuss this unique association between Guillain-Barrè syndrome, pericarditis, and nephrotic syndrome after infuenza vaccination.Tis further implicates the administration of infuenza vaccine with a higher risk of complications-not merely limited to one presentation at a time.
It is encouraging to note that most reported cases in the literature exhibit a favorable prognosis, with pericarditis typically resolving with anti-infammatory therapy.However, a caveat exists for patients with a history of pericarditis.Teir susceptibility to recurrent pericarditis following  subsequent infuenza vaccinations should be meticulously considered.Te immunization history of such patients becomes a pivotal aspect of their medical record, particularly when chest pain is their chief complaint.Terefore, any decision to administer further vaccinations must be a collaborative process involving both the patient and their healthcare provider.Tis collaborative approach ensures that patients are adequately informed of the potential risks and benefts, allowing them to make informed decisions.

Conclusion
In summation, while pericarditis remains a rare side efect of infuenza vaccination, the existence of recurrent cases in the literature emphasizes the importance of a patient's medical history, especially in instances where pericarditis is a prior diagnosis.Our case report illustrates a 91-year-old-female who presented with symptoms of acute pericarditis with signifcant elevations in infammatory markers three days after receiving infuenza vaccine.Her chest pain gradually resolved with colchicine and NSAID treatment.Tis case is essential in enhancing our understanding of potential side efects of vaccination and contributes to the ongoing discourse surrounding infuenza vaccine safety.It is incumbent upon healthcare providers to engage patients in informed discussions regarding the infuenza vaccine and any associated concerns.Vigilant monitoring of post-vaccination symptoms is equally vital to facilitate the early recognition and appropriate management of pericarditis, thereby ensuring the best possible outcomes for patients.Tis multifaceted approach to managing vaccine-induced pericarditis emphasizes the evolving landscape of vaccine safety and the ongoing need for healthcare professionals to remain informed and responsive to emerging clinical data.

Figure 1 :
Figure 1: ECG obtained upon arrival to the emergency department with no ischemic changes.

Figure 2 :
Figure 2: Subsequent ECG obtained 14 hours after initial ECG as shown in Figure 1.Subsequent ECG demonstrating ST elevations in inferior leads with PR depressions.

Table 1 :
Laboratory values at initial presentation.