Please choose the correct answer to the question: A vaccine can prevent a serious disease. When a new vaccine is developed, it is given to a small group of people. Why would it be important to test each vaccine on a small group of people before everyone can have one?

Answer1: to figure out how much the vaccine is worth Answer2: to determine how the vaccine will affect people Answer3: to understand how that disease affects the human body Answer4: to find out how many people are affected by the disease

Answer format: answer1/answer2/answer3/answer4
Answer: answer2