The effectiveness of the influenza vaccine varies from year to year. Each year the vaccine contains only the three strains of influenza that researchers feel are mostly likely to be circulating in the upcoming flu season. The decision on which strains to include has to be made months in advance in order to produce the millions of doses required. Sometimes the experts make a wrong choice, and the viral strains in the vaccine do not exactly match the strains in the community. Thus, the effectiveness of the vaccine can vary from 50 percent to over 95 percent depending on the match.
- What is influenza and what kind of health problems does the influenza virus cause?
- How is influenza transmitted and how likely is our child to get influenza?
- What kind of vaccine for influenza exists and when is it usually given?
- How serious and how common are the side effects of the influenza vaccine?
- What are the medical reasons to not give the influenza vaccine?