Researchers reported in the New England Journal of Medicine (August 14, 2014) that a high dose flu vaccine was more effective than the standard flu vaccine for seniors. The vaccine is called Fluzone High Dose vaccine. Of course, the media jumped on this report. In the Healthday article, the chief medical office for Sanofi-Pasteur—the Big Pharma company who funded the study—stated, “The study demonstrated a 24 percent reduction in influenza illness among the participants who received the high-dose vaccine compared to those who received the standard dose.”
To date, no flu vaccine has shown any significant efficacy in seniors. A 24 percent reduction in influenza illness in seniors would certainly be something to celebrate.
When medical students and residents rotate through my office, the first thing I do is hand them an article and ask them to explain the statistical methods used by the researchers. Over the years, I have had one student/doctor who understood statistics enough to understand how research articles are reported. I always tell the students/doctors that if they don’t know how to properly read the original research articles, they cannot make a proper decision on whether the particular therapy is useful or not.
After seeing the media article, I pulled the flu research article and read it. Here are the results: 31,989 participants were enrolled form 126 research centers in the U.S. and Canada. Half were given the standard flu vaccine and half given the high dose vaccine.
1.4% of the seniors who received the high dose vaccine became ill with the flu and 1.9% of the seniors who received the standard flu vaccine developed the flu.
(I hope you are not laughing as I did when I read that.)
How in the world did they report a 24% lowered incidence of the flu with the use of the high-dose vaccine? Simply dividing 1.4% by 1.9% gives the relative risk reduction of 24%. However, this is a relative risk reduction—a useless number to use when deciding whether a therapy is good for any patient.