Today's Morbidity and Mortality Weekly Report confirms that this flu season's vaccine has been less effective in patients than in most past years. The CDC estimates that getting vaccinated has reduced a person's risk of having to go to the doctor for influenza by 23 percent this year. Since the agency began making estimates in 2004-2005, they have ranged from 10 percent to 60 percent, so this is toward the low end.
Why the limited effectiveness? One culprit is H3N2. H3N2 viruses have been predominant this year, and some strains have “drifted” from the H3N2 vaccine virus. Those variants did not appear until after the vaccine composition for this year for the Northern Hemisphere had been selected.
In the meantime, a moderately severe flu season proceeds, and the CDC continues to recommend that people get vaccinated despite the circulation of the drifted viruses; the vaccine still prevents some infections, and it can reduce the severity of disease.
How has the influenza season been in your neck of the woods? How has it affected your institution and your lab?
