Vaccine Q&A General: What’s the difference between Tdap and DTaP? What does measles do to the immune system? Why do we keep getting the flu? What really causes autism? What does stress do the immune system? Is natural immunity to the chicken pox better when it comes to immunity? How do I talk to my kids about vaccines? Why do we need booster shots? Can the flu vaccine make you sick? Vaccine Shedding: Should You Really Be Concerned? What’s the difference between combination and simultaneous vaccines? Can your baby’s immune system handle more than one vaccine at a time? Why do we need to keep vaccinating if the disease is “gone”? How do vaccines work?