Microorganisms and Disease
The influenza vaccine is administered each year because

mutations in the viral hemagglutinin may allow the virus to evade the immune response elicited by previous vaccines
the vaccine is sufficiently toxic to make it necessary to administer only a small amount at any one time
None of these
it is a polysaccharide vaccine that does not confer long-term protection

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Microorganisms and Disease
Prontosil is

an effective antibacterial both in animals as well as in in-vitro cultures
an effective antibacterial when used in in-vitro cultures
an effective antibacterial when used in animals
not used as an antibacterial agent

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