The flu vaccine is not as good as most people believe. This time of year public health officials are putting on a full court press to vaccinate children, older people and those with chronic diseases. Influenza is especially cruel to these groups. The Centers of Disease Control and Prevention has extended its guidelines to include all Americans older than six months.
Researchers combed the medical literature between 1967 and 2011. After reviewing over 5,000 articles they narrowed the analysis to 31 of the very best studies. These trials actually confirmed influenza infection through culture or a more sophisticated laboratory test. In the gold-standard randomized-controlled trials, the pooled efficacy was 59%. There was surprising variability in effectiveness from year to year. In some years, effectiveness was as low as 16% while other years it rose to 76%.
These trials did not include young children or senior citizens. Although older people are the most vulnerable to complications and death from influenza, there is not enough data to determine how effective flu shots are in this age group. The authors conclude with a plea for more effective vaccines that can protect a greater number of people from influenza infection.
[The Lancet Infectious Diseases, online Oct. 26, 2011]