As the 2014-2015 influenza season winds down, we can start surveying the damage it caused. The season began in October, accelerated rapidly through November, and peaked, rather early for influenza, in the last week of December. January and February saw slow declines in the number of positive flu tests, but what’s interesting is that the number of hospitalizations due to influenza rose during those two months, peaking at the end of February. Why is that?

A simple explanation might be that when a virus is the predominant cause of sickness in a given community, less testing is done because less is needed. In other words, it’s often safe to assume that if an illness looks, sounds and feels like what’s circulating in the community, it’s a good bet it is, and testing is not necessary. So even though the number of positive flu tests peaked at the end of December, the actual number of cases of influenza peaked later — probably in early-to-mid February.

Children under five years old accounted for the highest group of pediatric hospital admissions. The most common underlying medical conditions in these children were asthma, neurologic disorders, and immune suppression.  Like most seasons, adults 65 years and older were hit the hardest by far, accounting for the most hospitalizations and deaths — the most ever recorded in this age group since 2005, when surveillance began. Underlying medical conditions in adults over 65 were led by cardiovascular disease, followed by metabolic disorders (like diabetes), and obesity. Of note, 7% of hospitalized adults and 39% of hospitalized children had no identified underlying conditions.

By February 21, the CDC reported that 92 children from 31 states died from influenza or its complications (mostly pneumonia):

10 children were aged <6 months, 15 were aged 6–23 months, 14 were aged 2–4 years, 30 were aged 5–11 years, and 23 were aged 12–17 years. Of the 92 deaths, 43 were associated with an influenza A (H3N2) virus infection, 40 deaths were associated with an influenza A virus infection that was not subtyped, six deaths were associated with an influenza B infection, two deaths were associated with an influenza A and B coinfection, and one death was associated with an influenza virus for which the type was not determined. Since influenza-associated pediatric mortality became a nationally notifiable disease in 2004, the total number of influenza-associated pediatric deaths has ranged from 37 to 171 per season; excluding the 2009 pandemic, when 358 pediatric deaths were reported to CDC during April 15, 2009, through October 2, 2010.


The good news from this passing influenza epidemic is that resistance to antiviral medications did not emerge. The bad news is that antiviral medications, like the prescription oseltamivir (Tamiflu), are very expensive and not very well tolerated in children (abdominal pain, nausea, vomiting, headaches, and irritability). They are also overprescribed. Antivirals for influenza should be reserved for those most at risk for developing infection (with prophylaxis after exposure) or complications: Children under 2, adults 65 and older, and anyone with significant underlying conditions (like the ones mentioned above).

Another reason why this was such a dangerous flu season was due to the relative ineffectivess of this year’s flu vaccine (only 23% effective) because of an “antigenic drift” (mutation) of the virus’ DNA last spring. Robert Roos says the FDA has been watching what’s going on in the Southern Hemisphere this winter in order to predict what strains next year’s influenza vaccine should contain:

VRBPAC member Janet Englund, MD, added, “It’s incredibly important to see what’s going on in Asia and the Southern Hemisphere; we know it drifts westward and northward. A really high proportion of those viruses come to us next.”


Last week, the Food and Drug Administration’s Vaccines and Related Biological Products Advisory Committee (VRBPAC) voted to recommend the influenza strains for the 2015-2016 influenza vaccine. What’s in?:

Trivalent Vaccines:

  • A/California/7/2009 (H1N1)pdm09-like virus
  • A/Switzerland/9715293/2013 (H3N2)-like virus
  • B/Phuket/3073/2013-like virus


Quadrivalent Vaccines:

  •  In addition to the 3 strains mentioned above,
    B/Brisbane/60/2008-like virus


What’s out of next year’s vaccine?:

  • B/Yamagata strain
  • B/Massachusetts strain


For those people who didn’t receive an influenza vaccine this year for themselves or their children, the only thing I can say is, “You’re lucky.” Maybe you got sick with influenza but recovered uneventfully. Maybe you didn’t get sick at all. Maybe you didn’t spread the virus to someone else with an underlying medical condition, at high risk for dying from influenza. Then again, maybe you did.

Like I said: you’re lucky. Don’t push it. Get a flu shot next Fall, and every Fall, to protect yourself, the ones you love, and the ones you’ve never even met, from a common and dreadful disease.


(Chart: CDC)