7.2 The Immune System and Vaccines

Notes

The immune system defends the body against pathogens.

• First lines of defense: skin, mucus, tears and stomach acid.
• Inside the body, white blood cells attack pathogens. Antibodies are proteins that target a specific pathogen.
• After an infection, memory cells help the body respond faster next time. This is immunity.
• A vaccine trains the immune system by showing it a harmless piece or a weakened or inactive form of a pathogen. The body makes antibodies and memory cells without getting the full disease.
• Vaccines have prevented diseases like polio, measles and whooping cough. Common vaccines for teens include Tdap, meningococcal and HPV, plus a yearly flu shot.
• Herd immunity: when most of a community is immune, the disease spreads less, protecting people who cannot be vaccinated, such as babies and people with weakened immune systems.
• Vaccines may cause mild side effects, such as a sore arm or a low fever, and serious side effects are very rare. Ask a doctor with questions.