When Should I get a Flu Shot?

Flu Shot: When is the Right Time to Get It? Dear Dr. Mahler: I am curious when is the best time to get a flu shot. Previously, I would get the shot as soon as they became available in early October. However, my doctor suggested that I wait until mid-November. What do you think? I have COPD and am doing OK over the past few years. My COPD medications include Spiriva and Advair with ProAir as needed. Cassandra from Perth Amboy, NJ Dear Cassandra: Influenza, commonly called flu, is a serious disease that can lead to hospitalization and sometimes even death. Every flu season is different, and influenza infection can affect people differently. The flu vaccine protects against the influenza viruses that testing indicates will be most common during the upcoming season. The usual flu vaccines (called “trivalent”) are made to protect against three flu viruses; an influenza A (H1N1) virus, an influenza A (H3N2) virus, and an influenza B virus. In addition, there is a high-dose trivalent vaccine recommended to those 65 years of age and older. A “quadrivalent” flu vaccine protects against four flu viruses that includes the same viruses as the trivalent vaccine plus an additional B virus. How does the flu shot work? Flu vaccines cause antibodies (proteins) to develop in the body about two weeks after vaccination. These antibodies provide protection against infection with the viruses that are in the vaccine. In a study published online on October 2015 in the Journal of the American Medical Association, researchers found that the flu vaccine reduced the risk of the flu (fever, muscle aches, tiredness) as well as pneumonia associated with the flu virus. When should I get the flu shot?  Flu outbreaks can happen as early as October, while in most seasons flu activity peaks in January or later. Since it takes about two weeks after vaccination for antibodies to develop in the body, I agree with your doctor and suggest that it is preferable to wait until mid-November.  However, if the flu virus occurs early in your local community, then you should get the flu shot right away. Which flu shot should I get? That depends on which vaccines are available where you get your flu shot. Some specialists recommend the high-dose trivalent flu shot for those 65 or older, and the quadrivalent vaccine for those under 65 years of age. Certainly, you should discuss this with your health care professional. Can I get the flu even if get the vaccine? Yes, it is still possible for you to get the flu even if you got vaccinated. The ability of flu vaccine to protect depends on your overall health and  the “match” between the viruses used to make the vaccine and those actually in the community. If they are closely matched, the vaccine should be quite effective. If they are not closely matched, vaccine effectiveness can be reduced like in 2014. However, even if the viruses are not closely matched, the vaccine can still prevent flu-related complications. This protection is possible because antibodies made in response to the vaccine can provide cross-protection against different but related influenza viruses. It most important that you do get the flu shot, and ideally before the flu virus appears in your community. No one can be sure about this until it actually happens.

Donald A. Mahler, M.D. is Emeritus Professor of Medicine at Geisel School of Medicine at Dartmouth in Hanover, New Hampshire. He works as a pulmonary physician at Valley Regional Hospital in Claremont, NH, where he is Director of Respiratory Services.