Question:

Hi I wonder what the difference between northern and southern hemisphere flu vaccine. Which one is better?

Answer:

Northern and southern hemispheres experience winter and flu season at opposite times of the year. So while we are having summer here in the United States, the southern hemisphere is experiencing their winter flu season. Because of this difference, the flu shots for each hemisphere are different as scientists try to predict which strains are most likely to affect a specific hemisphere during the upcoming flu season. 

Influenza vaccines contain three different strains of the influenza virus, either attenuated live virus (nasal mist) or inactive virus (shot). The selection of which strains will be included as one of those three is based on data collected by organizations like the World Health Organization (WHO). WHO releases recommendations for virus strains to be included in the vaccine every February for the northern hemisphere vaccine, and September for the southern hemisphere vaccine. The accuracy of this prediction determines how effective the flu shot is for that season. Therefore, you should receive the flu shot designed for the hemisphere in which you live so that you are protected against the strains of the virus predicted to impact your hemisphere.  This will provide you with better protection against the flu virus most likely to impact your area. 

You can read more at the WHO website: http://www.who.int/csr/disease/influenza/qanda_vaccinerechow.pdf 

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