Immunization; Infection

Influenza virus is a significant pathogen in pediatric solid organ transplant (SOT) recipients. However, these individuals respond poorly to standard-dose (SD) inactivated influenza vaccine (IIV). Recent studies have investigated two strategies to overcome poor immune responses in SOT recipients: (1) administration of high-dose (HD)-IIV compared to SD-IIV and (2) two doses of SD-IIV compared to one dose of SD-IIV in the same influenza season. One study compared HD-IIV vs. SD-IIV in adult SOT recipients and noted that HD-IIV was safe and more immunogenic; however, the median post-transplant period was 38 months. A phase I pediatric study comparing a single dose of HD-IIV vs. SD-IIV was safe with higher immunogenicity, but the study was limited by small sample size and median post-transplant vaccine administration was 26 months. In another phase II trial of adult SOT recipients, two doses of SD-IIV one month apart compared to one-dose of SD-IIV revealed modestly increased immunogenicity when given at a median of 18 months post-transplant. Therefore, these studies lack both evaluation in the early post-transplant period and substantive pediatric populations. Additionally, the administration of two-doses of HD-IIV in the same influenza season has not been evaluated in pediatric SOT recipients. Thus, the optimal immunization strategy for pediatric SOT recipients less than 24 months post-transplant is unknown. In addition, immunologic predictors and correlates of influenza vaccine immunogenicity in pediatric SOT recipients have not been well-defined. The central hypothesis of our proposal is that pediatric SOT recipients 1-23 months post-transplant who receive two doses of HD-quadrivalent inactivated influenza vaccine (QIV) will have similar safety but higher Hemagglutination Inhibition (HAI) geometric mean titers (GMTs) to influenza antigens compared to pediatric SOT recipients receiving two doses of SD-QIV.

The purpose of this study is to find out whether the COVID pandemic has affected participants' current physical activity, fitness, blood pressure, sleep, and mental stress to better understand its long-term health effects. To complete this study, participants will visit the Neurovascular Physiology Laboratory (NVPL) at the Indiana University School of Public Health Bloomington two times, requiring a total commitment of about 6 hours. Visit 1 involves completing screening questionnaires, a consent document, and additional questionnaires about participant health behaviors (e.g., sleep and physical activity) and general mental and physical health. After the visit, participants will also start tracking their sleep and physical activity using wearable devices for 14 days, diet for at least 3 days, and blood pressure and urine for 24 hours. Visit 2 is a second data collection visit, where participants will return the wearable devices. The investigators will measure participants' body composition, take measures of their cardiovascular health, and participants will complete a fitness test on a stationary cycle (exercise bike). The investigators will collect a 24 hour urine sample and take a blood sample to measure participants' blood glucose, electrolytes, hydration biomarkers, and markers of inflammation, as well as to study immune cells. The investigators will take participants' blood pressure at rest and during a hand-in-cold water test, which helps assess how participants' nervous system responds to stress. A full-body scan will measure participant body composition including bone density, muscle mass, and body fat percentage. Finally, participants will complete a cycling test that gradually increases in intensity to measure cardiovascular fitness. Risks involve potential pain or bruising from blood draws, discomfort from blood pressure cuffs, stress from vigorous cycling, and psychological stress from questionnaires. There's also a slight risk of severe cardiovascular events occurring during exercise and loss of data confidentiality. Finally, the cold water test may result in a rare but noted situation where the body's nervous system overreacts to the cold stimulus, leading to a drop in blood pressure and heart rate. Participants will be monitored by trained staff during all procedures to ensure safety.

The goal of this clinical trial is to assess the immune response to the yellow fever vaccine 17D in adults with prior 17D vaccination. The main questions this study aims to answer are: * how does prior vaccination affect antibody responses to re-vaccination? * how does prior vaccination affect the immune cell response to re-vaccination? Participants will: * have been previously vaccinated with 17D. * be re-vaccinated with 17D. * provide medical and travel histories. * provide a blood sample prior to vaccination * provide a blood sample approximately every other day for 14 days after vaccination. * provide a blood sample approximately 28 days after vaccination. * complete a daily diary of symptoms following vaccination for 14 days. * report any additional symptoms after 14 days.

Title: Impact on quality of life and disease burden in adults with herpes zoster Prospective cohort study for the primary objective and the secondary objectives (1 and 2) and retrospective cohort study for the secondary objective 3. Disease or disorder under study: Patients with a herpes zoster (HZ) diagnosis.

The goal of this observational study is to evaluate the protective effect of immune barrier on secondary infection after COVID-19 (coronavirus disease 2019) vaccination or COVID-19 virus Omicron B A. 5.2 strain infection by dynamically monitoring the COVID-19 antibody titer, cellular immune function and the occurrence of secondary infection of healthy participants, mainly medical staff in our hospital, to understand the cross protective effect of COVID-19 antibody on different variants of Omicron, and explore the best time to use COVID-19 vaccine to strengthen immunity after Omicron mutant infection.