C) Why are vaccines important in preventing infections of more dangerous viruses?

Vaccines are important in order to prevent infections of more dangerous viruses because with the help of vaccine body makes antibodies which helps in protecting the body against viruses.

Explanation:

There is no medicine present in vaccines. Vaccine contains dead virus which is injected in the body. When the immune system detect these viruses, they make antibodies that are effective in controlling the virus. When these viruses attack again, the body is prepared for it.