From "Infectious Diseases in Children":http://www.idinchildren.com/200402/survey.asp
2003-04 flu vaccine may not prevent ILI
The 2003-2004 influenza vaccine may be doing a poor job protecting against influenza-like illness (ILI), although further studies are needed to determine the vaccine’s effectiveness against laboratory-confirmed influenza, according to the CDC.
The Colorado Department of Public Health and Environment and The Children’s Hospital of Denver spearheaded a survey of 3,100 hospital employees to determine how well the 2003-2004 influenza vaccine protected against ILI. The survey asked whether the employee had been vaccinated this year and whether the employee was suffering from symptoms compatible with influenza.
Out of the 1,886 respondents to the survey, 1,424 reported having received the vaccine, and 389 reported ILI symptoms. Two separate analyses – a categorical analysis and a person-time analysis – were used to determine the vaccine’s effectiveness against ILI. According to the study, the vaccine was between 0% and 14% effective in preventing ILI.
The researchers cautioned that ILI is an imperfect measure of influenza activity, making it likely the survey underestimated the vaccine’s effectiveness against influenza.
There was speculation that because a drift strain (A/Fuijan) circulated widely across the United States, the vaccine would provide inadequate protection against influenza. However, the survey did not require medical verification of illness, so there is no way of telling whether that strain was a factor.
Editor’s note: The criteria for ILI were so broad as to include many illnesses that were not caused by influenza virus during a time of year when there are many other respiratory illnesses that fulfill the ILI criteria.
Thus, whatever the effect the vaccine might have had, and admittedly this is an imperfect vaccine, would have been diluted out by these ILIs that were not due to influenza. This is similar to estimating the effectiveness of pneumococcal vaccine on ear infections. We know that pneumococcus causes ear infections as do many other organisms. The vaccine can prevent most ear infections caused by pneumococcus and have an imperceptible effect on ear infections. I believe we will have to wait for a more critical analysis to assess the vaccine’s effectiveness. — Philip A. Brunell, MD
For more information:
CDC. Preliminary assessment of the effectiveness of the 2003-2004 inactivated influenza vaccine – Colorado, December 2003. MMWR. 2004;53(1):8-11.
I have to wonder--if the vaccine doesn't prevent flu-like illness, which was the big selling point in the first place (not missing work and such) what is the damn point? According to the study, the vaccine was between 0% and 14% effective in preventing ILI
is hardly acceptable.