Myopericarditis After COVID-19 Booster Dose Vaccination.

COVID-19 vaccine boosters were recommended by the Centers for Disease Control (CDC) for all populations ≥18 years to provide better protection against circulating variants. The risk of myopericarditis after sequential COVID-19 vaccination needs to be evaluated. We have demonstrated that the Vaccine Safety Datalink rapid cycle analysis method identified a lower incidence of myopericarditis after COVID-19 mRNA vaccine, in part because their search for hospital discharge claims omitted International Classification of Diseases, Tenth Revision codes, and because insurance claims from community hospitals may be delayed by weeks. We provide a more timely and complete case ascertainment of myopericarditis after COVID-19 booster vaccine in populations aged 18 to 39 years.

We studied a cohort of 65,785 Kaiser Permanente Northwest Health Plan members aged 18 to 39 years who received a COVID-19 vaccine booster at least 5 months after completion of the primary series. We identified cases of myopericarditis by searching the electronic health record for the National Center for Health Statistics text label for “myocarditis” or “pericarditis” diagnosis codes in all inpatient and outpatient encounters through January 18, 2022. The cohort was followed for 21 days after their booster. We excluded anyone with a documented diagnosis of myocarditis or pericarditis before their first COVID-19 vaccination. Two physicians independently reviewed the identified patient records and applied the CDC myocarditis and pericarditis surveillance case definition to classify records as confirmed, probable, or excluded on the basis of the previous published definition. Kaiser Permanente's institutional review board approved the study.

Our method identified 6 patients who met the confirmed or probable CDC case definition for acute myocarditis or pericarditis within 21 days of receiving the COVID-19 booster dose among 65,785 eligible members (Table 1 ). A total of 4 cases occurred in 27,253 men. All 6 patients received a Pfizer vaccine as their booster dose. A total of 5 of 6 patients reported chest pain within 4 days of vaccination, although 1 patient waited until Day 8 to present for her chest pain. Patient number 6 developed chest pain, myocarditis, and cardiogenic shock after his booster dose. Though the illness was attributed to the booster dose, his clinicians are concerned that the dose unmasked an underlying autoimmune condition. Additionally, patient number 5 presented with mild myocarditis after a heterologous series of Johnson & Johnson vaccine followed by a booster dose of Pfizer vaccine.

Table 1

Summary of myopericarditis cases following COVID-19 booster dose

Case	Age (years)	Sex	Primary series	Boost vaccine	Dose	Interval: Prime series to boost (days)	Chest pain onset (days)	EKG: ST elevation	Trop peak (mcg/L)	LVEF on echo	LOS (days)
1	18-24	M	Pfizer	Pfizer	3	204	3	+	2.93	55-60%	2
2	18-24	M	Pfizer	Pfizer	3	260	3	+	Trop I10.4	55%	1
3	25-29	M	Pfizer	Pfizer	3	210	3	+	10.4	60%	1
4	30-39	F	Pfizer	Pfizer	3	239	2	+	< 0.01	55%	1
5*	18-24	F	J&J	Pfizer	2	196	4	+	.04	60-65%	ED
6*	30-39	M	Pfizer	Pfizer	3	183	19	–	17.8	35-40%	4

LVEF = left-ventricular end-systolic function; LOS = length of stay; ED = emergency department; Pfizer = Pfizer BioNTech; J&J = Johnson and Johnson.

Normal troponin range: <=.03 mcg/L.

Met CDC case definition, atypical presentation.

Overall, we estimated 9.1 cases (exact 95% confidence interval [CI] 3.4 to 19.9) of post-booster myopericarditis per 100,000 booster doses given. In men, we estimated 14.7 cases (exact 95% CI 4.0 to 37.6) per 100,000 booster doses given.

We identified a risk of 9.1 cases per 100,000 booster doses. Our small sample size limits the precision of our estimate. This risk is higher than previous estimates reported by Vaccine Adverse Event Reporting System which identified 54 preliminary reports of vaccine-related myopericarditis; 12 confirmed and 38 under review, after 26.3 million booster doses administered across all ages, with an unadjusted estimate of 0.21 cases per 100,000 doses (95% CI 0.15 to 0.27). Vaccine Adverse Event Reporting System is passive system relying on patients or providers to report; but limitations include both over- and under-reporting. Active surveillance by the Vaccine Safety Datalink has not yet reported a risk of myopericarditis after booster vaccinations, although we would anticipate underestimation because of limitations in their methods. Israel reported the risk of myopericarditis after booster dose as 4.7 cases per 100,000 in men aged 20 to 24.

Myopericarditis occurs after booster doses and may be underreported by current surveillance methods. Completeness or high sensitivity of these case estimates are essential when modeling risk and benefit for wide-scale vaccine implementation and sequential COVID-19 vaccinations for the general population.

Disclosures

The authors have no conflicts of interest to declare.