Background: Influenza (flu) vaccinations are required for all NIH staff members who have direct contact with patients. COVID-19 vaccines are recommended for persons 6 months of age and older. Researchers want to learn about immunity in NIH staff members who get a flu and/or COVID-19 vaccine.

Objective: To understand what happens to the body s immune system throughout the year after getting the flu and/or COVID-19 vaccine.

Eligibility: Adults ages 18 and older who work at NIH and plan to get the current season s flu vaccine and/or COVID-19 vaccine.

Design: Participants will not get any vaccines as part of this study. Participants will be screened with a medical history and medicine review. They will get a survey via email. It will ask about their flu and SARS-CoV-2 history and vaccinations. Participants will have 12 monthly visits at NIH. If during that year they get both flu and SARS-COV-2 vaccines, their participation will be extended. Once a month, participants will be contacted. They will discuss any new medicines, recent vaccinations, or changes in medical history. Once a month, participants will have blood drawn. Once a month, participants will have nasal sampling. A small, flat absorptive strip will be placed in the nostril to soak up mucus. Participants will press against the outside of their nostril with their finger for 1 minute. Participants may be able to collect samples at home and mail them to NIH if they are not able to visit in person. Participation will last for about 12 13 months.