The North American vaccine is developed each year to work against three strains of influenza virus, based on trends seen in the Southern Hemisphere. The best time for vaccination is early October to mid-November. Anyone who is in contact with high-risk populations (including health care workers) should also receive the vaccine.
People who are not part of the high-risk groups but just want to avoid the flu can also get vaccinated. If you are currently sick with a low-grade fever, experts suggest that you should wait until you are better before you get the vaccine. If you do not have a fever, you do not have to wait.
Vaccinations are not recommended for children less than 6 months of age because their immune systems are too immature for the vaccine to work properly.
People who have an egg or chicken protein allergy, an allergy to any of the ingredients of the vaccine (e.g., formaldehyde, gentamicin), a history of allergic reactions to the flu vaccine, or an acute illness should not receive the vaccine.