The purposes of this study were to evaluate the relationship between risk factors for cardiovascular disease (CVD) and cardiac mass and function on cardiac magnetic resonance imaging (MRI), and to investigate possible risk factors for silent myocardial infarction (SMI) in an asymptomatic Asian population. We included 647 asymptomatic subjects (485 males, mean age 54.8 ± 6.7 years; 162 females, mean age 55.2 ± 7.6 years) who underwent 1.5-T cardiac MRI during a health checkup. The association between biventricular functional parameters as evaluated on MRI and CVD risk factors was examined using multivariable regression and analysis of variance. The left ventricular mass-to-volume ratios were positively related to body mass index (β = 0.153, p < 0.001), systolic (β = 0.165, p = 0.001) and diastolic (β = 0.147, p = 0.002) blood pressure, triglyceride levels (β = 0.197, p = 0.006), and C-reactive protein levels (β = 0.130, p < 0.001), and were negatively related to estimated glomerular filtration rates (β = -0.076, p = 0.025). No significant relationship was present between ventricular parameters and the presence of SMI after adjusting for confounders. The prevalence (6.9 %, 7/101) of SMI in diabetics was significantly greater than that in non-diabetics patients (0.9 %, 5/546; confidence interval 1.739-12.848; p < 0.001). Traditional CVD risk factors are associated with ventricular mass, geometry and function in asymptomatic subjects. Silent MI may not independently influence ventricular mass and function and diabetes mellitus may contribute to the development of SMI.

IntroductionDespite vaccine development, the COVID-19 pandemic is ongoing due to immunity-escaping variants of concern (VOCs). Estimations of vaccine-induced protective immunity against VOCs are essential for setting proper COVID-19 vaccination policy.MethodsWe performed plaque-reduction neutralizing tests (PRNTs) using sera from healthcare workers (HCWs) collected from baseline to six months after COVID-19 vaccination and from convalescent COVID-19 patients. The 20.2% of the mean PRNT titer of convalescent sera was used as 50% protective value, and the percentage of HCWs with protective immunity for each week (percent-week) was compared among vaccination groups. A correlation equation was deduced between a PRNT 50% neutralizing dose (ND50) against wild type (WT) SARS-CoV-2 and that of the Delta variant.ResultsWe conducted PRNTs on 1,287 serum samples from 297 HCWs (99 HCWs who received homologous ChAdOx1 vaccination (ChAd), 99 from HCWs who received homologous BNT162b2 (BNT), and 99 from HCWs who received heterologous ChAd followed by BNT (ChAd-BNT)). Using 365 serum samples from 116 convalescent COVID-19 patients, PRNT ND50 of 118.25 was derived as 50% protective value. The 6-month cumulative percentage of HCWs with protective immunity against WT SARS-CoV-2 was highest in the BNT group (2297.0 percent-week), followed by the ChAd-BNT (1576.8) and ChAd (1403.0) groups. In the inter-group comparison, protective percentage of the BNT group (median 96.0%, IQR 91.2–99.2%) was comparable to the ChAd-BNT group (median 85.4%, IQR 15.7–100%; P =0.117) and significantly higher than the ChAd group (median 60.1%, IQR 20.0–87.1%; P &lt;0.001). When Delta PRNT was estimated using the correlation equation, protective immunity at the 6-month waning point was markedly decreased (28.3% for ChAd group, 52.5% for BNT, and 66.7% for ChAd-BNT).ConclusionDecreased vaccine-induced protective immunity at the 6-month waning point and lesser response against the Delta variant may explain the Delta-dominated outbreak of late 2021. Follow-up studies for newly-emerging VOCs would also be needed.

Since its first emergence in late 2019, severe acute respiratory syndrome coronavirus-2 has claimed more than 6.5 million lives worldwide and continues to infect hundreds of thousands of people daily. To combat this once-in-a-century disaster, several vaccines have been developed at unprecedented speeds. Novel vaccine platforms (messenger ribonucleic acid vaccines and adenoviral vector vaccines) have played a major role in the current pandemic. In Korea, six vaccines, including a domestically developed recombinant vaccine, have been approved. As in other countries, vaccines have been proven to be safe and highly effective in Korea. However, rare serious adverse events and breakthrough infections have undermined public trust in the vaccines, even while the benefits of vaccination far outweigh the risks. The rise of the omicron variant and the subsequent increase in excess mortality demonstrated that while vaccines are a key component of the pandemic response, it alone can fail without non-pharmaceutical interventions like masking and social distancing. The pandemic of coronavirus disease has revealed both the strengths and weaknesses of our healthcare system and pandemic preparedness. When the next pandemic arrives, improved risk communication and vaccine development should be prioritized. To enable timely vaccine development, it is essential to make strategic and sufficient investments in vaccine research and development.