Consider these words from the Centers for Disease and Control (CDC):
The adjusted, age-stratified VE [vaccine effectiveness] point estimates were 58% for persons aged 6 months–17 years, 46% for persons aged 18–49 years, 50% for persons aged 50–64 years, and 9% for persons aged ≥65 years.
http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6207a2.htm?s_cid=mm6207a2_e
Although influenza vaccines are the best tool for prevention of influenza currently available, more effective vaccines are needed.
http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6202a4.htm?s_cid=mm6202a4_w