Okay kiddo, so a subunit vaccine is a type of medicine that helps to protect our bodies from getting sick. You know how our body has these tiny soldiers called antibodies that fight viruses and bacteria that make us sick? So, subunit vaccines prepare our body to make these antibodies even before we get exposed to the virus or bacteria. This way, if the real bad germs come to attack us, our body is already prepared and can fight them off quickly.
But how does it work? So, when we get sick, our body develops antibodies to fight off the germs causing the illness. A subunit vaccine is like a practice test for our body before it faces the real exam. Instead of giving us the entire virus, they only give us a tiny piece of it which is the "subunit" that can't make us sick but still helps our body recognize the enemy. So our body creates antibodies to fight off the "subunit" and remembers how to produce the same antibodies when facing the actual virus or bacteria. This is like your teacher giving a sample question for you to practice and remember when the actual test comes.
Pretty cool, huh? So, subunit vaccines are safe and effective because they do not give us the whole virus, only the tiny piece that prepares our body for the real fight. So when we get vaccinated, we are actually protecting ourselves and the people around us from getting sick.