Influenza: High-dose vaccine may reduce inflammatory heart disease risk in seniors

In a recent study, Danish researchers compared the effects of high-dose inactivated influenza vaccine (HD-IVV) with those of standard-dose inactivated vaccine (SD-IVV) on myocarditis and pericarditis in people over 65. The results found the incidence of myocarditis or pericarditis was lower in those who received VII-HD.In a secondary analysis of the DANFLU-2 randomized trial conducted on 332,438 participants aged 65 and older in Denmark during the 2022-23, 2023-24 and 2024-25 flu seasons, a team from the department of cardiology at Copenhagen University Hospital examined the risk of myocarditis or pericarditis associated with high-dose HD-IVV compared to SD-IVV.Participants were randomly assigned to receive either a high-dose quadrivalent inactivated influenza vaccine (60 mcg of hemagglutinin antigen per strain) or a standard-dose quadrivalent inactivated influenza vaccine (15 mcg). Of these, 1,295 had a history of myocarditis or pericarditis, including 97 with myocarditis and 1,218 with pericarditis.People with a history of myocarditis or pericarditis were older (mean age 74.2 years versus 73.7 years for those without a history), more often male (68.3% versus 51.3%), and had a higher prevalence of comorbidities such as chronic cardiovascular disease (72.6% vs. 27.2%), atrial fibrillation (41.3% vs. 10.1%) and hypertension (37.9% vs. 19.2%).Lower incidenceDuring each study season, participants were followed from the 14th day after vaccination until May 31 of the following year. Events occurring before 14 days after vaccination were included in a sensitivity analysis.According to the results of the secondary analysis published in JAMA Network Open, the incidence of myocarditis or pericarditis was lower in those who received VII-HD compared to VII-SD (19 vs. 35 events), with a relative vaccine efficacy of 45.71% (95% CI, 2.46-70.67, P = 0.04). Furthermore, there were no cases of myocarditis among those in the high-dose vaccine group, compared with two cases in the standard-dose group.However, this study has several limitations: The small number of reported events, the lack of knowledge about the etiology and severity of each event, and the fact that the DANFLU-2 trial did not compare the effects of vaccines with no vaccine. In addition, “The generalizability to younger individuals, who generally have a higher risk of inflammatory heart disease, is also unknown,” the authors acknowledged.

Influenza: High-dose vaccine may reduce inflammatory heart disease risk in seniors

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