Vaccination against COVID-19: Quebec report confirms risk of myocarditis, pericarditis

A recently published Quebec surveillance report provided a comprehensive picture of myocarditis and pericarditis after COVID-19 vaccination. The report, from the Institut national de santé publique du Québec (INSPQ) and submitted to Quebec’s surveillance program for possible immunization side-effects (ESPRI), was based on surveillance data and also on an analysis of clinical-administrative data on emergency room visits or hospitalizations for myocarditis or pericarditis.“The results of this work confirm the presence of a significant increase in the risk of consultation or hospitalization for myocarditis or pericarditis in the 21 days following the administration of a second dose of vaccine and a third dose of mRNA vaccine,” concluded the authors, led by epidemiologist Isabelle Rouleau (PhD). They also point out that their results are “consistent with the rest of the epidemiological evidence” and that they support “decision-making within the Comité sur l'immunisation du Québec (CIQ), notably by making it possible to recommend the preferential use of Comirnaty® vaccine (from Pfizer-BioNTech) in children, adolescents and people under 30 years of age.”Between Dec. 20, 2020, and Dec. 31, 2022, some 19 million doses of COVID-19 vaccine were administered in Quebec. At the same time, 889 cases of myocarditis or pericarditis occurred within 42 days of vaccination and were reported to ESPRI. Of these, 386 (43%) were not retained for analysis by ESPRI researchers, either because the presence of myocarditis or pericarditis had been ruled out by medical evaluation (8%) or a normal cardiac workup (6%), because another diagnosis had been made to explain the manifestations observed (11%), or because a health professional had not evaluated the patient at the time symptoms were present (14%).Of the 503 cases selected, 47 (9%) of those vaccinated were under 18, 149 (30%) were aged 18 to 29, 81 (16%) were aged 30 to 39, and 226 (45%) were aged 40 or over at the time of diagnosis. Just over half were male (53%), and the average age of cases was around 40.“The vast majority of reported cases were temporally associated with mRNA vaccines, which were the most widely used during the campaign (96% of doses),” the report pointed out. In total, 326 cases (65%) were linked to the administration of the Comirnaty vaccine, and 163 (32%) to Moderna's Spikevax® vaccine. On the other hand, only 20 reports (3%) concerned the administration of the ChAdOx1 viral vector vaccine, marketed by AstraZeneca.With regard to the vaccination sequence, “The rate of myocarditis or pericarditis following the first dose (2.93 per 100,000 doses) is statistically comparable to that observed after the second (3.35), while the rate after the third dose is lower (0.95),” noted the INSPQ analysts. They point out that the rates observed in children aged 5 to 11 (0.50) were much lower than those observed in other age groups, while the highest rates are observed in 18- to 29-year-olds (5.96). “These results demonstrate that myocarditis and pericarditis are uncommon in children aged 5 to 11 and that vaccination does not appear to increase their risk.”Spikevax vs ComirnatyOverall, reporting rates for the Spikevax vaccine are slightly higher than those for Comirnaty (rate ratio [RR]: 1.13 [0.93-1.36]), “an effect that varies by age,” noted the report. “The highest difference between the two vaccines is observed in adults aged 18 to 29 (RT: 1.78 [1.28-2.48]) but tends to decrease and reverse with age.” Among people under 50, reporting rates were higher for Spikevax (RT: 1.47 [1.16-1.85]), while among people aged 50 and over, rates for Spikevax are lower than those for Comirnaty (RT: 0.65 [0.45-0.95]). Examination of clinical-administrative data shows that the rate of emergency room visits or hospitalization for myocarditis or pericarditis within 42 days of basic vaccination against COVID-19 is 7.70 per 100,000 doses, with the rate being 5.97 with the first dose, 8.99 with the second dose and 8.51 with the booster dose.“Rates among children aged 5 to 11 (0.62) are much lower than those observed in other age groups,” the report noted, with the highest rates found among 18- to 29-year-olds (12.83), “a trend that remains regardless of dose rank or vaccine type.” In addition, the results show “a significant increase in risk within 21 days of the second dose of mRNA vaccine, particularly in adolescents and adults under 30.”Rates of consultation, hospitalizationAmong people aged 40 and over, “The rate of consultation or hospitalization for myocarditis or pericarditis following administration of an mRNA vaccine is comparable to that of viral vector vaccines (RT: 1.03 [0.77-1.38]),” the report said. For all basic vaccinations (doses 1 to 3) of adults, these rates are slightly higher for Spikevax than for Comirnaty (RT: 1.14 [1.021.28]). However, “The only significant difference between the two vaccines is observed in adults aged 18 to 29 who received the second dose,” with the risk of consultation or hospitalization being almost three times higher with Spikevax (relative risk [RR]: 8.12 [3.90-16.9]) than with Comirnaty (RR: 2.93 [1.93-4.47]). In conclusion, the report's authors wrote that “the simultaneous analysis of passive surveillance data and data from Quebec clinical-administrative databases revealed the presence of a significant reporting bias, the magnitude of which varied according to age, sex, vaccine administered and dose rank.” In their view, passive surveillance remains essential for ongoing monitoring of the safety of vaccines administered in Quebec. However, “The application of sound epidemiological methods using Quebec clinical-administrative databases, free of reporting bias, remains crucial in assessing the risks associated with vaccination.”

Vaccination against COVID-19: Quebec report confirms risk of myocarditis, pericarditis

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