The h1n1 and h3n2 viruses both cause the flu, an infectious disease characterized by respiratory symptoms, fever, and body aches. each year, a flu vaccine that contains h1n1 and h3n2 antigens is developed. an individual who receives the vaccine makes antibodies directed against these antigens. the flu vaccine is typically about 60% effective against h1n1 flu viruses, but only 30% effective against h3n2 viruses. what is the most likely reason why the flu vaccine is less effective against the h3n2 flu viruses than the h1n1 flu viruses?