Clinical impact of influenza vaccination after ST- and non-ST-segment elevation myocardial infarction - insights from the IAMI trial

Risk of Cardiovascular Events after Influenza Infection-related Hospitalizations in Adults with Congenital Heart Disease -A Nationwide Population Based Study

BACKGROUND

Cardiovascular complications due to viral infection pose a significant risk in vulnerable patients such as those with congenital heart disease (CHD). Limited data exists regarding the incidence of influenza and its impact on cardiovascular outcomes among this specific patient population.

METHODS

A retrospective cohort study was designed using the Canadian Congenital Heart Disease (CanCHD) database - a pan-Canadian database of CHD patients with up to 35 years of follow-up. CHD patients aged 40 to 65 years with influenza virus-associated hospitalizations between 2010 and 2017 were identified and 1:1 matched with CHD patients with limb fracture hospitalizations on age and calendar time. Our primary endpoint was cardiovascular complications: heart failure, acute myocardial infarction, atrial arrhythmia, ventricular arrhythmia, heart block, myocarditis, and pericarditis.

RESULTS

Of the 303 patients identified with incident influenza virus-associated hospitalizations, 255 were matched to 255 patients with limb fracture hospitalizations. Patients with influenza virus-related hospitalizations showed significantly higher cumulative probability of cardiovascular complications at one year (0.16 vs. 0.03) and five years (0.33 vs. 0.15) compared to patients hospitalized with bone fracture. Time-dependent hazard function modeling demonstrated a significantly higher risk of cardiovascular complications within nine months post-discharge for influenza-related hospitalizations. This association was confirmed by Cox regression model (average hazard ratio throughout follow-up: 2.48; 95% CI: 1.59 - 3.84).

CONCLUSIONS

This pan-Canadian cohort study of adults with CHD demonstrated an association between influenza virus-related hospitalization and risk of cardiovascular complications during the nine months post discharge. This data is essential in planning surveillance strategies to mitigate adverse outcomes and provides insights into interpreting complication rates of other emerging pathogens, such as COVID-19.

Exploring the Relationship between Acute Coronary Syndrome, Lower Respiratory Tract Infections, and Atmospheric Pollution

Background: Respiratory infections were found to be connected with the incidence of acute coronary syndrome (ACS). The proposed pathway of this connection includes inflammation, oxidative stress, pro-coagulation, and atherosclerotic plaque destabilization. This can cause rapture and thrombus formation, leading to ACS. Our study aimed to assess the risk factors for coronary artery thrombosis as a manifestation of ACS and for lower respiratory tract infections (LRTIs) in patients with ACS. Methods: The study included 876 patients with ACS from January 2014 to December 2018. Both the clinical data and air pollution data were analyzed. Statistical tests used for analysis included Student's t-test, the Mann-Whitney U-test, the Chi-squared test, and the odds ratio Altman calculation. Results: LRTIs were found in 9.13% patients with ACS. The patients with LRTI had a higher risk of coronary artery thrombosis (OR: 2.4903; CI: 1.3483 to 4.5996). Moreover, they had increased values of inflammatory markers, were older, had a lower BMI, and a higher rate of atrial fibrillation. The average atmospheric aerosols with a maximum diameter of 2.5 μm (PM2.5 concentration) from three consecutive days before hospitalization for ACS were higher in patients with LRTI. Conclusions: The occurrence of coronary artery thrombosis was higher among the patients with LRTI during ACS. PM2.5 exposition was higher in the three consecutive days before hospitalization in patients with LRTI during ACS.

Association of respiratory infections and the impact of vaccinations on cardiovascular diseases

Influenza, pneumococcal, severe acute respiratory syndrome coronavirus 2, and respiratory syncytial virus infections are important causes of high morbidity and mortality in the elderly. Beyond the burden of infectious diseases, they are also associated with several non-infectious complications like cardiovascular events. A growing body of evidence in prospective studies and meta-analyses has shown the impact of influenza and pneumococcal vaccines on types of cardiovascular outcomes in the general population. Influenza vaccination showed a potential benefit for primary and secondary prevention of cardiovascular diseases across all ages. A reduced risk of cardiovascular events for individuals aged 65 years and older was associated with pneumococcal vaccination. Despite scientific evidence on the effectiveness, safety, and benefits of the vaccines and recommendations to vaccinate elderly patients and those with risk factors, vaccination rates remain sub-optimal in this population. Doubts about vaccine necessity or efficacy and concerns about possible adverse events in patients and physicians refer to delayed acceptance. Vaccination campaigns targeting increasing professional recommendations and public perceptions should be implemented in the coming years. The aim of this review paper is to summarize the effect of vaccination in the field of cardiovascular disease to achieve a higher vaccination rate in this patient population.

Pleiotropic Effects of Influenza Vaccination

Influenza vaccines are designed to mimic natural influenza virus exposure and stimulate a long-lasting immune response to future infections. The evolving nature of the influenza virus makes vaccination an important and efficacious strategy to reduce healthcare-related complications of influenza. Several lines of evidence indicate that influenza vaccination may induce nonspecific effects, also referred to as heterologous or pleiotropic effects, that go beyond protection against infection. Different explanations are proposed, including the upregulation and downregulation of cytokines and epigenetic reprogramming in monocytes and natural killer cells, imprinting an immunological memory in the innate immune system, a phenomenon termed "trained immunity". Also, cross-reactivity between related stimuli and bystander activation, which entails activation of B and T lymphocytes without specific recognition of antigens, may play a role. In this review, we will discuss the possible nonspecific effects of influenza vaccination in cardiovascular disease, type 1 diabetes, cancer, and Alzheimer's disease, future research questions, and potential implications. A discussion of the potential effects on infections by other pathogens is beyond the scope of this review.