Fine Needle aSpiration of Lymph nodEs to Study vAccine-induced Immunity

Study Summary: This study looks at how the body responds to a pneumonia (S. pneumoniae) vaccine. **Fine Needle Aspiration (FNA)** is used to take a small sample from a **lymph node**, a part of the immune system that helps fight infections. This helps us understand how vaccines work, which can make future vaccines better.

Key Points:

• Duration: The study lasts 3 months with 8 times of blood and lymph node checks.
• Participants: Healthy people aged 20-40, without certain health issues.
• Procedures: You will get one vaccine shot, and have samples taken from your blood and lymph nodes.

To join, you must be aged 20-40 and healthy, but you can't join if you are pregnant, breastfeeding, or have had certain vaccines or infections. The study uses **spectral flow cytometry**, a special test that looks at cells, to measure immune cells called **B cells**. These cells are important because they help protect the body from infections.📈