Incidence, Severity, and Mortality of Influenza During 2010-2020 in Korea: A Nationwide Study Based on the Population-Based National Health Insurance Service Database

Safety and Influenza Infections in Children Aged 6-35 Months Receiving Cell Culture-Derived Inactivated Quadrivalent Influenza Vaccine During the 2023-2024 Influenza Season in South Korea

BACKGROUND/OBJECTIVES

Influenza poses a significant risk for young children, particularly those under five. Cell culture-derived influenza vaccines offer advantages in reducing adaptive changes and mitigating egg allergy concerns. SKYCellflu® quadrivalent has been in use since 2015, and this study aimed to assess its safety and influenza infections in children aged 6-35 months in South Korea.

METHODS

A prospective cohort, non-interventional, multi-center post-marketing surveillance study was conducted from 2020 to 2024. This study presents data from the 2023-2024 influenza season on safety and influenza infections in children aged 6-35 months following SKYCellflu® vaccination. Safety was assessed based on adverse events (AEs) within 28 days post-vaccination, and influenza infections were assessed via phone calls or medical record screening.

RESULTS

Among 333 safety set participants, 54.4% reported at least one AE, with most being mild to moderate. The cumulative incidence of influenza infections among 247 ad hoc subsets was 4.5%, and the incidence rate was 1.3 per 100 person-months (95% CI, 0.7-2.4) during the 2023-2024 influenza season. The two-dose regimen in vaccine-naïve infants aged 6-11 months showed a lower cumulative incidence of influenza infection rate (0.8% vs. 3.8%) and incidence rate (0.3 vs. 0.9 per 100 person-months) than the one-dose group (3.8%). No influenza-related hospitalizations occurred within the ad hoc subset.

CONCLUSIONS

This study demonstrated a tolerable safety profile and the pattern of influenza infections following SKYCellflu® vaccination. Additionally, the two-dose regimen was associated with a lower incidence of influenza infections, suggesting potential benefits in enhancing protection among infants aged 6-11 months.

Knowledge, attitude, practice, and barriers among physicians in the Middle East and North Africa region toward influenza vaccination for the high-risk group of patients: a cross-sectional study

BACKGROUND

The influenza vaccine is a cost-effective measure to reduce morbidity and mortality, especially for high-risk patients. Healthcare providers have an essential role in patients' education about vaccines. This study aims to examine physicians' understanding, perceptions, and practices regarding influenza vaccination in the Middle East and North Africa (MENA) region for high-risk patients.

METHODS

We conducted a multinational cross-sectional study in 21 countries in MENA region from July 10th to September 10th, 2023. Data were collected using an online self-administered survey distributed through different social media platforms. We used a valid questionnaire designed to determine the knowledge, attitude, and practice of physicians toward influenza vaccination. A multivariable binomial logistic regression analysis was conducted to identify significant predictors for offering the influenza vaccine.

RESULTS

In this study, which involved 2017 physicians (the mean (SD) age was 29 (± 6.2); 52% were males), the majority expressed a low to medium level of knowledge about influenza vaccination, with only 4% displaying a high level of knowledge. Regarding attitude, the majority (n = 1511, 74.9%) were quite concerned. However, only (n = 509, 25.4%) offered the vaccine to patients. The main predictors for offering the vaccine were age (adjusted odd ratio (AOR) = 1.036, 95%CI = 1.003-1.07, p = 0.031), male sex (AOR = 1.39, 95%CI = 1.09-1.77, p = 0.007), living in upper-middle-income countries (AOR = 3.14, 95%CI = 2.1-4.7, p < 0.001), having PhD degree (AOR = 3.15, 95%CI = 1.47-6.71, p = 0.003), being a senior resident (AOR = 2.005, 95%CI = 1.147-3.5, p = 0.015), working two to five shifts per week (AOR = 1.55, 95%CI = 1.02-2.35, p = 0.04), working more than five shifts per week (AOR = 1.75, 95%CI = 1.06- 2.88, p = 0.027), attitude (AOR = 1.33, 95%CI = 1.243- 1.44, p < 0.001), following these practices regarding influenz vaccination with the other office staff: Encourage and offer (AOR = 5.73, 95%CI = 4.11- 8.007, p < 0.001), require but do not offer (AOR = 3.73, 95%CI = 2.59- 5.38, p < 0.001), and require and offer the influenza vaccine (AOR = 6.79, 95%CI = 4.88- 9.45, p < 0.001) to the office staff. The main barriers to influenza vaccination were unawareness of vaccine availability (32%), cost (25%), and forgetfulness (23.4%).

CONCLUSIONS

Approximately half of the physicians were knowledgeable about the flu vaccine, but practice was deficient and impeded by barriers like unawareness and forgetfulness.

State of the Art and Emerging Technologies in Vaccine Design for Respiratory Pathogens

In this review, we present the efforts made so far in developing effective solutions to prevent infections caused by seven major respiratory pathogens: influenza virus, respiratory syncytial virus (RSV), the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), Bordetella pertussis, Streptococcus pneumoniae (pneumococcus), Mycobacterium tuberculosis, and Pseudomonas aeruginosa. Advancements driven by the recent coronavirus disease 2019 (COVID-19) crisis have largely focused on viruses, but effective prophylactic solutions for bacterial pathogens are also needed, especially in light of the antimicrobial resistance (AMR) phenomenon. Here, we discuss various innovative key technologies that can help address this critical need, such as (a) the development of Lung-on-Chip ex vivo models to gain a better understanding of the pathogenesis process and the host-microbe interactions; (b) a more thorough investigation of the mechanisms behind mucosal immunity as the first line of defense against pathogens; (c) the identification of correlates of protection (CoPs) which, in conjunction with the Reverse Vaccinology 2.0 approach, can push a more rational and targeted design of vaccines. By focusing on these critical areas, we expect substantial progress in the development of new vaccines against respiratory bacterial pathogens, thereby enhancing global health protection in the framework of the increasingly concerning AMR emergence.

Cost-effectiveness of the adjuvanted quadrivalent influenza vaccine for older adults in South Korea

South Korea's National Immunization Program administers the quadrivalent influenza vaccine (QIV) to manage seasonal influenza, with a particular focus on the elderly. After reviewing the safety and immune response triggered by the adjuvanted QIV (aQIV) in individuals aged 65 and older, the Ministry of Food and Drug Safety in Korea approved its use. However, the extensive impact of aQIV on public health is yet to be fully understood. This study assessed the cost-effectiveness of replacing QIV with aQIV in South Korean adults aged 65 years and older. A dynamic transmission model, calibrated with national influenza data, was applied to compare the influence of aQIV and QIV on older adults and the broader population throughout a single influenza season. This study considered both the direct and indirect effects of vaccination on the elderly. We derived the incremental cost-effectiveness ratios (ICERs) from quality-adjusted life-years (QALYs) and costs incurred, validated through a probabilistic sensitivity analysis with 5,000 simulations. Findings suggest that transitioning to aQIV from QIV in the elderly would be cost-effective, particularly if aQIV's efficacy reaches or exceeds 56.1%. With an ICER of $29,267/QALY, considerably lower than the $34,998/QALY willingness-to-pay threshold, aQIV presents as a cost-effective option. Thus, implementing aQIV with at least 56.1% efficacy is beneficial from both financial and public health perspectives in mitigating seasonal influenza 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.

Analysis of the incidence of influenza before and after the COVID-19 pandemic in South Korea

OBJECTIVES

Influenza outbreaks of varying size occur every year, but during the COVID-19 pandemic, many countries experienced influenza at lower levels. However, following the relaxation of COVID-19 prevention measures in 2022, the incidence of influenza began to increase gradually. Thus, this study compared the occurrence of influenza from week 36 of 2017, before the COVID-19 outbreak, until 2023.

METHODS

The analysis was conducted using influenza-like illness occurrence data available from the Korea Disease Control and Prevention Agency infectious disease website. Additionally, to examine the changes in COVID-19 and influenza occurrence during the pandemic, COVID-19 incidence data from 20 January 2020 to 31 August 2023 were obtained from the KDCA Coronavirus Disease 19 homepage.

RESULTS

During the COVID-19 pandemic, which corresponds to the 2020/2021 and 2021/2022 influenza seasons, there was no seasonal influenza epidemic, and the incidence rates were below the usual outbreak levels. However, in the 2022/2023 season, when the spread of COVID-19 had eased, a seasonal pattern similar to that observed before the COVID-19 pandemic was noted. Furthermore, correlation analysis between the rates of influenza-like illness and COVID-19 incidence showed no significant correlation during the entire period. However, a significant correlation emerged in 2023 (r = 0.393, p <0.05). These results suggest that influenza was suppressed during the COVID-19 pandemic but returned to typical seasonal patterns after the COVID-19 prevention policies were eased.

CONCLUSION

The positive correlation observed between the incidences of COVID-19 and influenza in 2023 indicates that COVID-19, no longer a novel pandemic-causing infectious disease, may have transitioned to an endemic pattern similar to seasonal influenza.

COVID-19 Vaccination Strategies in the Endemic Period: Lessons from Influenza

Coronavirus disease 2019 (COVID-19) is a highly contagious zoonotic respiratory disease with many similarities to influenza. Effective vaccines are available for both; however, rapid viral evolution and waning immunity make them virtually impossible to eradicate with vaccines. Thus, the practical goal of vaccination is to reduce the incidence of serious illnesses and death. Three years after the introduction of COVID-19 vaccines, the optimal vaccination strategy in the endemic period remains elusive, and health authorities worldwide have begun to adopt various approaches. Herein, we propose a COVID-19 vaccination strategy based on the data available until early 2024 and discuss aspects that require further clarification for better decision making. Drawing from comparisons between COVID-19 and influenza vaccination strategies, our proposed COVID-19 vaccination strategy prioritizes high-risk groups, emphasizes seasonal administration aligned with influenza vaccination campaigns, and advocates the co-administration with influenza vaccines to increase coverage.

Convolutional LSTM-LSTM model for predicting the daily number of influenza patients in South Korea using satellite images

OBJECTIVES

Influenza affects a considerable proportion of the global population each year, and meteorological conditions may have a significant impact on its transmission. In this study, we aimed to develop a prediction model for the number of influenza patients at the national level using satellite images and provide a basis for predicting influenza through satellite image data.

STUDY DESIGN

We developed an influenza incidence prediction model using satellite images and influenza patient data.

METHODS

We collected satellite images and daily influenza patient data from July 2014 to June 2019 and developed a convolutional long short-term memory (LSTM)-LSTM neural network model. The model with the lowest average of mean absolute error (MAE) was selected.

RESULTS

The final model showed a high correlation between the predicted and actual number of influenza patients, with an average MAE of 5.9010 per million population. The model performed best with a 2-week time sequence.

CONCLUSIONS

We developed a national-level prediction model using satellite images to predict influenza incidence. The model offers the advantage of nationwide analysis. These results may reduce the burden of influenza by enabling timely public health interventions.