An attack brought on by the presence of the influenza virus in the body produces a temporary immunity, but, unfortunately, the protection is against only the type of virus that caused the influenza. Because the disease can be produced by any one of three types, referred to as A, B, or C and many varieties within each type, immunity to one virus will not prevent infection by other types or strains.
Protection from the influenza virus is also complicated by the fact that immunity to a specific virus persists for less than a year. Finally, because a virus may periodically change characteristics, the problem of mutation makes it difficult to carry out a successful immunization program. Vaccines are often ineffective against newly evolving strains.
An attack brought on by the presence of the influenza virus in the body produces a temporary immunity, but, unfortunately, the protection is against only the type of virus that caused the influenza. Because the disease can be produced by any one of three types, referred to as A, B, or C and many varieties within each type, immunity to one virus will not prevent infection by other types or strains.Protection from the influenza virus is also complicated by the fact that immunity to a specific virus persists for less than a year. Finally, because a virus may periodically change characteristics, the problem of mutation makes it difficult to carry out a successful immunization program. Vaccines are often ineffective against newly evolving strains.
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