A comparison of epidemiology and clinical outcomes between influenza A H1N1pdm09 and H3N2 based on multicenter surveillance from 2014 to 2018 in South Korea

Real-world effectiveness of influenza vaccine over a decade during the 2011-2021 seasons-Implications of vaccine mismatch

BACKGROUND

Influenza imposes a significant healthcare burden in Korea, leading the government to initiate a national immunization program. Previous studies on vaccine effectiveness (VE) were limited to single-season estimation in Korea.

METHODS

This multicenter prospective cohort study enrolled patients with influenza-like illnesses at 10 medical centers in Korea from 2011 to 2021. The demographic and clinical data were collected from questionnaire surveys and electronic medical records. Using a test-negative design, we aimed to investigate the effectiveness of a seasonal influenza vaccine for antigenic matching of the vaccine and circulating viral strains over 10 seasons.

RESULTS

Overall, 5322 adults aged ≥65 years were enrolled. Only three (33.3 %) of nine seasons showed >70 % antigenic match between vaccine and circulating strains. Influenza VE was significantly variable by season, ranging from -46.9 % (95 %confidence interval [CI]: -127.6-5.2) in the 2011/12 season to 47.7 % (95 %CI: 22.6-64.7) in the 2016/17 season. A significant difference was observed in the VE depending on whether the vaccine strains matched with epidemic strains: 28.8 % (95 %CI: 8.8-44.8) in matched seasons versus -12.0 % (95 %CI: -30.0-3.7) in mismatched seasons. Across the study period, influenza-related hospitalizations were reduced by 13.6 % (95 %CI: 0.7-24.8) with vaccination. In a subgroup analysis, the VE against influenza-related hospitalization was 48.4 % (95 %CI 29.6-62.2) in A/H3N2 dominant seasons and 53.8 % (95 %CI: -73.4-87.7) in A/H1N1 dominant seasons, respectively.

CONCLUSION

Influenza vaccine mismatch was frequent over the study period, leading to negligibly low VE in mismatched seasons. Influenza vaccination reduces the risk of influenza-related hospitalizations.

Alterations of pathogen transmission patterns and attenuated immune stimulation might be the cause of increased adult respiratory infections cases in 2023, results from a multi-center study in mainland China

Background

Several respiratory infections outbreaks have been observed in mainland China after reduction of non-pharmaceutical interventions. Other countries have seen increases in respiratory infections outside typical seasons post-COVID-19, warranting investigation into underlying causes.

Methods

We established monitoring networks for suspected respiratory infection in 14 tertiary hospitals nationwide. PCR for SARS-CoV-2, influenza A and B were performed on 3708 respiratory specimens and deep sequencing were conducted to identify co-infections or newly emerging microbes in 2023. Viral evolutionary analysis was completed. We retrospectively detected serum antibody level for various respiratory pathogens from 4324 adults without respiratory infections over 7 years to observe its dynamic curves.

Findings

SARS-CoV-2 and influenza A were the main pathogens during outbreaks in 2023, bacterial-virus and bacterial-bacterial co-infections were most detected, but community co-infections didn't significantly increase pneumonia incidence. Different SARS-CoV-2 and influenza variants were present in different outbreaks, and no novel pathogens were found. The epidemiological patterns of influenza A, COVID-19 and etc. were altered, exhibiting characteristics of being "staggered" compared to most global regions, and potentially led to "overlapping prevalence". Binding antibody testing showed regular fluctuation, without significant decrease against common respiratory pathogens in adults. Influenza A antibody stimulation was attenuated during the 2023 outbreak.

Conclusions

"Misaligned" alteration in seasonal respiratory disease patterns possibly caused combined epidemics, leading to cases spike in China, 2023. In adults, antibody levels didn't show significant decline, but reduced immune response to influenza during 2020-2023 emphasizes the need for consistent vaccination during pandemics.

Comparative Analysis of Clinical Outcomes Using Propensity Score Matching: Coronavirus Disease 2019 vs. Seasonal Influenza in Korea

BACKGROUND

The advent of the omicron variant and the formulation of diverse therapeutic strategies marked a new epoch in the realm of coronavirus disease 2019 (COVID-19). Studies have compared the clinical outcomes between COVID-19 and seasonal influenza, but such studies were conducted during the early stages of the pandemic when effective treatment strategies had not yet been developed, which limits the generalizability of the findings. Therefore, an updated evaluation of the comparative analysis of clinical outcomes between COVID-19 and seasonal influenza is requisite.

METHODS

This study used data from the severe acute respiratory infection surveillance system of South Korea. We extracted data for influenza patients who were infected between 2018 and 2019 and COVID-19 patients who were infected in 2021 (pre-omicron period) and 2022 (omicron period). Comparisons of outcomes were conducted among the pre-omicron, omicron, and influenza cohorts utilizing propensity score matching. The adjusted covariates in the propensity score matching included age, sex, smoking, and comorbidities.

RESULTS

The study incorporated 1,227 patients in the pre-omicron cohort, 1,948 patients in the omicron cohort, and 920 patients in the influenza cohort. Following propensity score matching, 491 patients were included in each respective group. Clinical presentations exhibited similarities between the pre-omicron and omicron cohorts; however, COVID-19 patients demonstrated a higher prevalence of dyspnea and pulmonary infiltrates compared to their influenza counterparts. Both COVID-19 groups exhibited higher in-hospital mortality and longer hospital length of stay than the influenza group. The omicron group showed no significant improvement in clinical outcomes compared to the pre-omicron group.

CONCLUSION

The omicron group did not demonstrate better clinical outcomes than the pre-omicron group, and exhibited significant disease severity compared to the influenza group. Considering the likely persistence of COVID-19 infections, it is imperative to sustain comprehensive studies and ongoing policy support for the virus to enhance the prognosis for individuals affected by COVID-19.

COVID-19 Disease Course in Former Smokers, Smokers and COPD Patients

The severe respiratory and systemic disease named coronavirus disease-2019 (COVID-19) is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Currently, the COVID-19 pandemic presents a huge social and health challenge worldwide. Many different risk factors are associated with disease severity, such as systemic arterial hypertension, diabetes mellitus, obesity, older age, and other co-infections. Other respiratory diseases such as chronic obstructive pulmonary disease (COPD) and smoking are common comorbidities worldwide. Previous investigations have identified among COVID-19 patients smokers and COPD patients, but recent investigations have questioned the higher risk among these populations. Nevertheless, previous reports failed to isolate smokers and COPD patients without other comorbidities. We performed a longitudinal evaluation of the disease course of smokers, former smokers, and COPD patients with COVID-19 without other comorbidities, from hospitalization to hospital discharge. Although no difference between groups was observed during hospital admission, smokers and COPD patients presented an increase in COVID-19-associated inflammatory markers during the disease course in comparison to non-smokers and former smokers. Our results demonstrated that smoking and COPD are risk factors for severe COVID-19 with possible implications for the ongoing pandemic.

A comparison of epidemiology and clinical outcomes between influenza A H1N1pdm09 and H3N2 based on multicenter surveillance from 2014 to 2018 in South Korea

BACKGROUND

After pandemic, A(H1N1)pdm09 is generally known to be associated with younger adults' infection and greater severity than seasonal A(H3N2) but some inconsistences between recent studies exist.

OBJECTIVES

We aimed to compare the epidemiology and clinical outcomes of A(H1N1)pdm09 and A(H3N2) to verify and consolidate about the knowledge of known differences of subtypes.

METHODS

Data were retrospectively collected from the hospital-based influenza morbidity and mortality surveillance in South Korea in nine tertiary care hospitals, from August 31, 2014, to August 25, 2018. Patients with H1N1pdm09 or H3N2 infection admitted in the emergency room or ward were recruited.

RESULTS

A total of 1747 patients had influenza A and were divided into two groups those with A(H1N1)pdm09 (n = 240) and those with A(H3N2) (n = 1507). A(H1N1)pdm09 group had younger age (mean age ± standard deviation 50.0 ± 18.8 in H1N1 vs 53.4 ± 21.1 in H3N2, P = .030), lower influenza vaccination (27.9% vs 43.9%, P < .001) and pneumococcal vaccination rates (41.0% vs 51.9%, P < .001), and fewer underlying diseases (67.5% vs 74.0%, P = .035) than the A(H3N2) group. Influenza A subtypes were not associated with pneumonia risk (adjusted odds ratios [AOR] of A(H1N1)pdm09: 0.7 [95% confidence interval [CI]: 0.4-1.2, P = .172]) and in-hospital mortality (hazard ratio (HR) of A(H1N1)pdm09: 1.0 (95% CI: 0.3-3.1, P = .983)). Influenza vaccination reduced in-hospital mortality in hospitalized patients (HR: 0.3 (95% CI: 0.1-0.7), P = .005).

CONCLUSIONS

A(H1N1)pdm09 infection was more common in younger patients without significant difference in pneumonia risk and in-hospital mortality between subtypes. Influenza vaccination was associated with reduced in-hospital mortality.