The viruses that cause influenza can change rapidly, and different strains may coexist at any given time. Influenza vaccines are thus developed each year to protect people from the three strains expected to be most prevalent. People are advised to receive the vaccine at the beginning of the 'flu season' since the immunity provided by the vaccine will wane after several months. For children between the ages of 6 months to 8 years, two doses of injection will be given at least one month apart to confer adequate protection, while for those over 8 years old one dose of injection will be adequate. Most people achieve protection from influenza vaccine approximately 1-2 weeks after receiving the immunization, so travellers should allow adequate time for vaccination before departure.
The vaccine is recommended for high-risk group, i.e. age 65 years or older, adults and children with chronic lung or heart problems, residents of nursing homes, those with chronic health problems or immunological deficits, and children and teenagers receiving long-term aspirin therapy.
It is also recommended for health care providers attending to high-risk people, and household members (including children) of persons who are in the high-risk group. The vaccine is also recommended for frequent travellers who do not want to contract influenza during travel/business.
Some may experience within 1-2 days mild local reaction - soreness at the injection site, or constitutional symptoms (low grade fever, dizziness, chills, malaise, headache, sweating, muscle aches). Most reactions/symptoms will subside within 1-2 days without intervention.
Vaccination is not recommended for the following groups:
- persons who are allergic to eggs or antibiotics especially neomycin;
- people with a fever or illness that is more than 'just a cold';
- women who are or might be pregnant;
- persons who have exhibited a moderate to severe reaction after a previous influenza shot.