Classify the following vaccines by type. Which could cause the disease it is supposed to prevent?
a. Attenuated measles virus
b. Dead Rickettsia prowazekii
c. Vibrio cholerae toxoid
d. Hepatitis B antigen produced in yeast cells
e. Purified polysaccharides from Streptococcus pyogenes
f. H. influenzae polysaccharide bound to diphtheria toxoid
g. A plasmid containing genes for influenza A protein

Step 2: Classify each vaccine based on the description: - a. Attenuated measles virus is a live attenuated vaccine because it uses a weakened form of the virus. - b. Dead Rickettsia prowazekii is an inactivated (killed) vaccine since the bacteria are killed. - c. Vibrio cholerae toxoid is a toxoid vaccine, which uses inactivated toxins to elicit immunity. - d. Hepatitis B antigen produced in yeast cells is a recombinant subunit vaccine, as it uses a specific antigen produced by genetic engineering. - e. Purified polysaccharides from Streptococcus pyogenes are polysaccharide vaccines, which use bacterial surface sugars. - f. H. influenzae polysaccharide bound to diphtheria toxoid is a conjugate vaccine, combining polysaccharide with a protein carrier to improve immune response. - g. A plasmid containing genes for influenza A protein is a DNA vaccine, which delivers genetic material to produce antigen in host cells.