Vaccination of healthy working adults has been shown to decrease absenteeism, and vaccination of children might prevent household spread of the disease. Vaccination during pregnancy is considered safe, and women in the second and third trimester of pregnancy who develop influenza have an increased risk of complications from the disease. Not recommended for use in children Large outbreaks of influenza usually do not occur before December in the USA and reach a peak in January or February but may continue into the spring. The duration of protection conferred by influenza vaccine generally begins one to two weeks after injection and may last six months or longer. The optimal time for vaccination is from October through mid-November, but any time from September to the end of the influenza season is appropriate.
Influenza vaccine is made from inactivated virus grown in eggs.
Except for soreness at the injection site for one or two days, adverse reactions are uncommon. Fever, myalgia and malaise can occur for one or two days, usually in young patients with no previous exposure to influenza antigens. Hypersensitivity reactions, presumably to egg protein, occur rarely. Whether influenza vaccine rarely causes Guillian-Barr syndrome remains controversial. Influenza vaccination may be advisable for healthy people as well as for elderly and high-risk patients and their contacts.