Title: Mucosal and systemic immunity correlates of protection against influenza in young children (MUSIC-Flu). The goal of this observational study is to better understand how immune responses in the blood and mucosa are linked to protection against influenza infection and illness in young children. We will compare immune responses in children who get influenza infection to those who do not.
Children aged 2-5 years of age will be followed from April through October 2026 during the influenza season in South Africa. During this time, nasal swabs will be collected three times per week to test for influenza and other respiratory viruses. Information on symptoms and temperature will be collected by nurses at weekly visits and daily by caregivers using an electronic symptom diary.
Blood samples will be collected before and after the influenza season, and at two additional time points during the study. Special immune cells will also be collected from blood samples before and after the season. In addition, samples from the nose and mouth will be collected every month. These samples will be tested to measure immune responses, including antibodies, signaling proteins (cytokines), and specific immune cells (T cells and B cells).
Children aged 2-5 years of age (i.e. from the second birthday until 5 years and 11 months of age) at the time of enrolment.
Healthy children as established by medical history and clinical examination before entering the study.
Parent availability and willingness to provide written informed consent to all study procedures
Child planning to reside in the selected community for the duration of the study.
Presence of malnutrition (defined as z score for age <-2 based on WHO child grown standard at time of screening for eligibility).
Presence of any serious systemic disorder determined by medical history and/or physical examination that would compromise the participant's health or is likely to result in non-conformance to the protocol or a child who is on treatment for any chronic medical condition.
Prior history of receiving influenza vaccination.
Not providing consent for storage and shipment of samples for immunological testing.
All health children aged 2 -5 years of age, residing in the Jouberton Township
Cohort
Prospective
Not listed
Geometric Mean Titers (GMT) (with 95% CIs) of systemic and mucosal immune markers at each scheduled time point, stratified by infection status (infected vs uninfected) Immune markers include systemic (neutralizing, hemagglutinin, IgM, and IgG) and mucosa
Time to first laboratory-confirmed influenza infection Association between immune marker levels and time to first influenza infection will be estimated using Cox proportional hazards regression, reported as hazard ratios with 95% confidence intervals.
Geometric Mean Titers (GMT) (with 95% CIs) of systemic and mucosal immune markers at each scheduled time point, stratified by PCR-confirmed influenza-like illness (ILI) status (symptomatic ILI infected vs symptomatic ILI uninfected)
Immune markers include systemic (neutralizing, hemagglutinin, IgM, and IgG) and mucosal (IgM, IgG, and IgA) anti-influenza antibodies.
Time to first laboratory-confirmed influenza illness Association between baseline immune marker levels and time to first influenza illness will be estimated using Cox proportional hazards regression, reported as hazard ratios with 95% confidence interval
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National Institute for Communicable Diseases, South Africa
Lead sponsor
Perinatal HIV Research Unit of the University of the Witswatersrand
Collaborator
Imperial College London
Collaborator
Centers for Disease Control and Prevention
Collaborator
