Answer:
12.A substance containing a weakend form of disease-causing germs that helps protect against certain diseases.
13.It causes white blood cells to produce antibodies which fight disease-causing germs.
14.
15.Hay fever
16.Anaphylaxis
17.970 thousand,44million
18. Acquired Immunodeficiency Syndrome, by weakening the immune system making it more vulnerable to diseases
Explanation:
