You should get your second dose as close to the recommended interval as possible. However, you should not get the second dose earlier than the recommended interval. There is no maximum interval between the first and second doses for either vaccine. Side effects might include a sore arm or flu-like symptoms and could affect your ability to do daily activities, but they should go away in a few days. Having flu-like symptoms means that your body is building an immune response which tells you that the vaccine is working. Unless a vaccination provider or your doctor advises against it, be sure to get the second dose even if you have side effects after the first dose. Also, please be aware that it takes time for your body to build protection after any vaccination. You are not fully protected until two weeks after your second Pfizer or Moderna dose.