When we go to the doctors, sometimes we get vaccinated (YUCK) but vaccinations are actually really good for our bodies to help fight harmful diseases . Vaccines work like a 'training' course for our immune system. Basically when our body gets infected by a foreign bacteria or virus (an antigen), it can sometimes take our body a few days to fight back and produce antibodies.
Unfortunately, a few days is way too long if we get nasty infections such as the measles. Infection can kill a person before our immune system can fight back. Despite this, our bodies become more efficient at fighting viruses and bacteria when we encounter it more than once. This is because our bodies produce a memory cell which remembers which antibody to produce when we encounter the same infection. This is where vaccines come in, vaccinations are made of dead or weakened antigens that can't cause any harm to our bodies but make our immune system identify it as an enemy. So, when our body produces antibodies in response, we are also able to produce memory cells which can fight off these diseases.
Therefore, when we come across the same disease again, our body is equipped to quickly strike it down. SO, get your vaccinations kids