Influenza vaccine

Influenza vaccines, also known as flu shots, are vaccines that protect against influenza. A new version of the vaccine is developed twice a year as the influenza virus rapidly changes. While their effectiveness varies from year to year, most provide modest to high protection against influenza. They decrease the number of missed days of work by a half day on average. Vaccinating children may protect those around them but the effectiveness of the vaccine in those over 65 years old is unknown because the evidence for this group is poor.