Answer:
below
Step-by-step explanation:
A vaccine works because when in the body it trains the immune system to recognize and fight off bacteria/viruses. Certain molecules will trigger an immune response, these molecules are called antigens. By having these antigens injected into the body, the immune system sees them as a safe invaders and start to produce antibodies. So when the immune system comes across a virus/bacteria it will attack before they can weaken the host. The immunity of the host depends if they have been given vaccines or not, no vaccines mean a weaker immune system.
(Sorry it has been a little while since I've done this, so my answer may be a bit iffy)