The influenza vaccine is administered each year because
A. mutations in the viral hemagglutinin may allow the virus to evade the immune response elicited by previous vaccines
B. it is a polysaccharide vaccine that does not confer long-term protection
C. the vaccine is sufficiently toxic to make it necessary to administer only a small amount at any one time
D. none of the above
Answer:A
The influenza vaccine is administered each year because
A. mutations in the viral hemagglutinin may allow the virus to evade the immune response elicited by previous vaccines B. it is a polysaccharide vaccine that does not confer long-term protection C. the vaccine is sufficiently toxic to make it necessary to administer only a small amount at any one time D. none of the above