How Healthy Adults Respond to the Nasal Flu Vaccine

This is a prospective interventional study evaluating mucosal immune and epithelial responses in healthy adults following administration of the FDA-approved live attenuated influenza vaccine (FluMist) given as an intranasal spray. Healthy volunteers aged 18 to 65 years who do not smoke and who meet eligibility criteria will be enrolled.

Participants will complete three study visits over approximately one week. At the first visit, informed consent, screening, baseline nasal swabs and nasal wash will be performed, followed by administration of FluMist. Follow-up nasal samples and safety assessments will be collected at approximately 2 and 4 days after vaccination.

Nasal samples will be analyzed using single-cell RNA sequencing, proteomics, and RT-qPCR to assess local immune, epithelial, and viral responses. Samples will be coded, stored under secure conditions, and retained for up to five years after study completion.

The objective of the study is to characterize early mucosal immune responses to FluMist vaccination and improve understanding of influenza vaccine-induced immunity at the site of infection.

Inclusion criteria

• Healthy adults aged 18 to 65 years
• Non-smokers (no smoking or vaping within the past 6 months)
• No chronic lung disease or significant chronic medical conditions
• No current or recent (within 1 month) upper or lower respiratory infection
• Able and willing to provide informed consent
• Have not received the current seasonal influenza vaccine
• Able to comply with study procedures and follow-up visits

Exclusion criteria

• Age under 18 or over 65 years
• Pregnancy or breastfeeding
• Prisoners
• Non-English speaking individuals
• Immunocompromised individuals (including HIV/AIDS, immunosuppressive therapy, chemotherapy, or primary immunodeficiency)
• Chronic medical conditions including asthma, chronic lung, liver, kidney, neurologic, hematologic, metabolic, or significant cardiovascular disease (except isolated hypertension)
• History of chronic sinusitis or significant nasal allergies requiring frequent or daily treatment
• Acute moderate or severe illness at time of enrollment, with or without fever
• Receipt of influenza vaccine during the current season or within the past 2 weeks
• Receipt of another live vaccine within 4 weeks prior to enrollment or planned during study period
• Use of influenza antiviral medications (e.g., oseltamivir, zanamivir) within 48 hours prior to vaccination or planned use within 14 days after vaccination
• History of severe allergic reaction to influenza vaccine or any component of FluMist (including egg allergy if applicable)
• History of Guillain-Barré syndrome following influenza vaccination
• Any condition that, in the opinion of the investigator, would interfere with study participation or interpretation of results