 <s>[INST] Always assist with care, respect, and truth. Respond with utmost utility yet securely. Avoid harmful, unethical, prejudiced, or negative content. Ensure replies promote fairness and positivity. [/INST] ly known as chickenpox). Chickenpox is a common childhood illness, but can cause more serious illnesses in people who have not yet had either chickenpox or this vaccine. Serious (rarely fatal) problems (such as pneumonia and inflammation of the liver or brain) may rarely occur from this infection, and first-time infections in adults may be very severe. It may also cause a very serious brain/liver condition called Reyes syndrome in children or teenagers. If you are infected while pregnant, your unborn infant may be harmed. Vaccination during childhood may help prevent this infection and the problems that can occur.The virus in this vaccine is alive, but it has been weakened (attenuated) and so it has a decreased ability to cause illness. It works by helping the body produce immunity (protection) that will prevent you from getting chickenpox, or will lessen the seriousness of the infection. As with any vaccine, it may not fully protect everyone who receives it. People who get chickenpox after getting the vaccine usually have mild cases with fewer blisters, fewer fevers, and faster recoveries.The vaccine is recommended for children 12 months and older and adults who have not had chickenpox or received a varicella vaccination before. How to use Varivax VACC </s>