The 2016-17 influenza season is turning out to be a fairly typical one (in other words, horrible for those who are sickened by the nasty virus). And this year’s vaccine, which protects against four different strains of the influenza virus, is pretty good. Not great, as Maggie Fox informs us, but pretty good:

“Interim influenza vaccine effectiveness estimates for the 2016-17 season indicate that vaccination reduced the risk for influenza-associated medical visits by approximately half,” a CDC team wrote in the agency’s weekly report on disease.

It lowered the risk of having to go to the hospital or the emergency room by 48 percent, the team calculated…


48 percent isn’t nothing. It’s certainly better than the 2014-15 influenza season that saw the virus mutate before arriving in the Northern Hemisphere. That year, the vaccine was barely 20% effective. In a great year, when the vaccine matched closely with circulating strains, 70-80% efficacy would be expected.

Among many, many other things, the Centers for Disease Control and Prevention keeps people like you and me updated on influenza’s progress throughout the flu season in their Weekly U.S. Influenza Surveillance Report. Here are some highlights (and lowlights) of the 2016-17 influenza season so far:

— At this moment, cases of influenza being reported to the CDC are rising (see graph above). By the middle of February, the number of cases has still not peaked. (Believe it or not, it’s still not too late to get a flu shot if you haven’t already.)

— Influenza A (H3N2) strain reigns supreme by far as the most prominent source of misery during this flu season, accounting for the vast majority of flu circulating in our communities this winter. Influenza B (Yamagata) and influenza B (Victoria) account for most of the rest of circulating flu strains. Influenza A (H1N1), which wreaked havoc in 2009-10, is a minor player this year.

— This year’s vaccine provides 43% protection against the influenza A (H3N2) strain (boo!), but 73% effectiveness for influenza B strains (yay!).

— Influenza A (H3N2) is not only the predominant strain, but also the strain that is causing the most severe symptoms. 93% of Americans hospitalized with influenza-associated illnesses have evidence of infection with this strain.

— It’s no surprise that the people most likely to be hospitalized due to influenza are adults older than 65 years, followed by adults aged 50-64, and then children 0-4 years of age.

— 95% of adults hospitalized so far have had at least one underlying medical condition — heart disease, metabolic disorders, and obesity being most commonly reported.

— 53% of hospitalized children had at least one underlying condition — asthma, neurologic disorder, chronic lung disease, and obesity are most commonly reported. (We should pause and note that 47% of hospitalized children thus far during this influenza season have no reported underlying medical conditions. Again, a reminder of the importance of providing influenza vaccines to all children each and every year.)

— In women of childbearing age who have been hospitalized with influenza, a third (33.3%) were pregnant. Research shows that influenza is especially harmful to the health of the mother, pregnancy outcomes, and fetal health.

— It’s early, but as of February 11 (the date of the last weekly report), 29 children have died from the flu in the U.S. this influenza season. Typically, pediatric deaths during a flu season range from 31-171, though in 2009-10, the H1N1 “swine flu” virus was identified as a killer of 358 children. Deaths due to flu in adults are much, much higher every year.


For more information and charts illustrating the progression of the 2016-17 influenza season, head to the CDC’s website and follow the Weekly U.S. Influenza Surveillance Report here.