Annual vaccination lowers the risk of flu infection but is more effective in some years than others because it is not always possible to predict exactly which strains of the virus are most prevalent. Despite varying results, vaccination is strongly recommended for people with health problems that put them at higher risk of severe flu complications like pneumonia. People at high risk are also urged to take an antiviral medication as soon as they start to feel flu symptoms. Starting on drugs early suppresses the virus before it has a chance to trigger more serious health problems.
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