The contraindications to receiving the vaccine are allergic reactions to previous flu shots or immediate allergy to eggs or egg-products. The side-effects of the shot are infrequent and not severe--including fever, tiredness, and muscle ache beginning 6-12 hours after the vaccination and persisting for 1 or 2 days. The vaccine is effective in preventing disease, but not against all flu strains. Even if you were vaccinated last year, it doesn't fully protect against the strains that might be a problem this year. Immunity does go down during the year following vaccination, so you need one shot every year to help be protected.
Once the decision is made to receive the flu vaccine, understand that children less than nine years of age who are receiving the flu vaccine for the first time need to have two doses administered at least one month apart. This allows these previously unvaccinated children to make appropriate amounts of antibody. One might also consider immunizing all people living in the home, so as to minimize flu exposure for everyone. Please check with your child's doctor if you think your child is a candidate for it. Now is the time to get the flu shot!