Influenza update


By Mark J. Ingerman, MD, FACP, Chief, Infectious Diseases and Chief, Infection Prevention and Control  


Influenza activity has been at elevated levels in the U.S. for eight weeks this season and continues to increase in some areas. The northwest part of the country experienced early flu activity and now seems to be decreasing. The Midwest and eastern coast of the country continue to experience increases in activity. The strain that has dominated influenza has been Influenza A H3N2. Over the last 15 years, flu seasons have averaged 13 weeks in length.


According to data from the U.S. Flu Vaccine Effectiveness Network, interim estimates show the flu vaccine has been approximately 48% effective in preventing Influenza A and B illness. The effectiveness of the vaccine has been higher for Influenza B than Influenza A.


With weeks to go during the current flu season, vaccination at this time still could offer protective benefits. It is common that Influenza B becomes more prominent at the end of the flu season. Influenza antiviral drugs still can be used as per CDC recommendations.


More efficacious vaccines for influenza are being experimentally evaluated on a regular basis. However, the influenza virus changes year to year with antigenic drift and antigenic shift. The genome of the virus also can change at irregular intervals. This makes the formulation of a live attenuated vaccine extremely difficult. Therefore, the efficacy of the influenza vaccine changes from year to year.


However, the CDC — as well as the Main Line Health Infectious Diseases Department and Infection Prevention Department — highly recommend influenza vaccination for your patient population. It will remain a mandatory requirement for employees at MLHS.


Although the influenza vaccine is far from perfect in preventing the influenza illness, one can use a simple analogy comparing getting the flu to being in a car accident. It is much safer to be in an accident (being infected with influenza) with safety belts on (having been vaccinated with influenza vaccine) as opposed to being in a car accident without safety belts (no influenza vaccine). Influenza causes considerable morbidity and mortality. The influenza vaccine can help mitigate or prevent these complications.


Please call the Infectious Diseases or Infection Prevention Department with any questions.


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