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What is Which vaccine strain is changed every yearly and explain in detail?
* Influenza virus has two impoant antigens: Haemagglutinin (H) and Neuraminidase (N) * These antigens undergo periodic antigenic variations * Major antigens variations are seen only with influenza A viruses and may be associated with pandemics - called as antigenic shifts. * Minor variations causing outbreaks are called as antigenic drifts. * Because of these variations, vaccines should be modified according to the current prevalent strain. Ref:- Harrisons T.B of internal medicine 19th edition; pg num:- 1209