Beyond the News: Flu facts and fallacies

February 16, 2018

Is there still time to protect yourself from this season’s virulent flu strains?

Absolutely, says Patricia Brown, M.D., F.A.C.P., F.I.D.S.A., professor of Internal Medicine for the Wayne State University of School of Medicine, and associate chief of staff for Medicine at the John D. Dingell VA Medical Center. We asked Dr. Brown — a recipient of the Laureate Award from the American College of Physicians — to set the record straight on such matters as why some people still get the flu even though they were vaccinated, whether the flu shot actually causes the flu and how the Wayne State Physician Group pulls out all the stops to protect patients from getting the flu.

Q: This season’s flu shot seemed like it did not provide adequate coverage for some strains of the illness. How is the flu shot devised each year? What institution decides which strains to guard against?

A: The World Health Organization and the U.S. Centers for Disease Control and Prevention review the data on the prevalent circulating strains and make a recommendation as to which should be included in the vaccine each year. Because there must be some lead time for vaccine manufacturers to make vaccines available to administer by September, this decision must be made by the spring for the following flu season — and depending on the timing of the flu season, the data available may not be complete.

This year's vaccine does include the correct strains, including the H3N2 strain that is causing the largest number of flu cases this year, but the protection the vaccine can provide for the H3N2 strain is not as high as the protection provided for other strains of influenza. From our knowledge of past flu seasons when the H3N2 strain has predominated, we know there are more hospitalizations and more deaths, especially among those older than 65 years of age and in young children when H3N2 influenza is the predominate strain circulating in the community.

Q: In a typical year, how many Americans will die of complications of the flu? Do you expect this year to reflect typical mortality rates?

A: The CDC published an analysis in 2016 which estimated that the number of deaths from influenza and associated complications was as low as 12,000 in 2011-12 to as high as 56,000 in 2012-13. This year, because the H3N2 strain is predominant, we will see deaths in the higher range.

Q: What do you say to people who refuse to get a flu shot because they think it causes the flu?

A: The flu vaccine is not a live-virus vaccine, so it is not possible to get the flu from vaccination. Many people note that they received the vaccine, yet just a short time later they got the "flu." It is important to understand that there are several dozen respiratory viruses that circulate during flu season — the vaccine only protects against influenza, so the illness experienced was likely due to another virus. There is a tendency, even among health care providers, to label all viral-type illnesses in the winter months as "flu," but this is not good practice — we should reserve the term "flu" for influenza.

Lastly, it is possible that someone could get influenza after the vaccine because it takes about two weeks to develop protective antibodies in response to the vaccine. The vaccine did not give you the flu; you did not have sufficient time to develop the protective antibody, and you caught the flu before the vaccine could protect you. Some vaccines only contain one strain of influenza B, and if the alternate strain is circulating, you may get influenza B despite having the vaccine. Increasingly, more vaccines contain both strains of influenza B. Finally, in years where there is not a good match between the vaccine and circulating strains, you may get flu despite getting the vaccine.

Q: What adjustments do you think will be made next year to provide wider protection from different strains?

A: I would anticipate that scientific effort will focus on how to develop a vaccine that can provide more effective coverage for the H2N2 strain of influenza.

Q: Can you describe the reasons behind several regions of the country — notably northern Florida — being subjected to a flu epidemic? How does that happen?

A: Although Florida is in the news because of a recent rapid increase in influenza cases, the number of states that CDC has designated as having high influenza activity increased from nine in December to 32 in January, and influenza is currently widespread in every state in the U.S. except Oregon. Again, we are experiencing a very bad flu season across the U.S.

Q: Do you still recommend the flu shot to your patients, even in January or February?

A: Absolutely. As of Feb. 3, the number of physician visits for influenza-like illness in our state was still on the increase, with the sharpest increase here in southeast Michigan. We do not know when flu season will end, so it is not too late to get the vaccine.

Even though preliminary data from this flu season and data from prior seasons when the H3N2 strain predominated shows that the vaccine is not highly effective at preventing H3N2, there is also interesting data that demonstrates that individuals who get the vaccine — even if they do get the flu — may be less likely to have a severe infection.

Q: Is there a group of individuals who should absolutely get the flu shot?

A: Everyone over the age of six months should get the flu shot. Older individuals, young children, pregnant women, individuals with chronic lung and heart disease, and individuals with compromised immune systems are most vulnerable.

Healthy individuals are most likely to mount a strong antibody response and be protected, so we will not pass the flu along to a more vulnerable individual for whom it could be a far more serious illness. This is why health care organizations, including the Wayne State University Physician Group, require all health care workers to get a flu shot. It's not just about us — it's about protecting our patients.