Today’s weekly national flu report had the following nugget of information under the virology section:
“41(48%) of the 85 H3N2 viruses tested have been characterized as A/Texas/50/2012-like, the influenza A (H3N2) component of the 2014-2015 Northern Hemisphere influenza vaccine. 44 (52%) of the 85 viruses tested showed either reduced titers with antiserum produced against A/Texas/50/2012 or belonged to a genetic group that typically shows reduced titers to A/Texas/50/2012. Among viruses that showed reduced titers with antiserum raised against A/Texas/50/2012, most were antigenically similar to A/Switzerland/9715293/2013, the H3N2 virus selected for the 2015 Southern Hemisphere influenza vaccine. A/Switzerland/9715293/2013 is related to, but antigenically and genetically distinguishable, from the A/Texas/50/2012 vaccine virus. A/Switzerland-like H3N2 viruses were first detected in the United States in small numbers in March of 2014 and began to increase through the spring and summer.”
This might all seem a bit complicated, but, lucky for us, the Centers for Disease Control and Prevention explains it thus:
“Second, flu shots could be less effective than usual because the viruses now beginning to spread around the country aren’t a good match for the ones used in the vaccine, according to the CDC, which sent out an emergency advisory to doctors last night.
Four influenza viruses are circulating, Frieden said. About half the H3N2 virus samples tested had major genetic differences from the ones in the vaccine. Other circulating flu viruses are good matches for those in the flu shot.”
The same article tells us about H3N2 viruses’ history of messing with us:
“First, the dominant strain of influenza virus in circulation is H3N2, a type that has doubled rates of hospitalizations and deaths in the past, especially among older people, very young children and people with chronic health conditions, said Thomas Frieden, director of the Centers for Disease Control and Prevention.”
Yeah, I flipped those quotes. They really should have been introduced in that order, but that’s just me.
Anyway, yes, H3N2 viruses cause prolonged and intense seasons while H1N1 cause sharp and intense seasons that seem to peak and go away relatively quickly. On the average and in the long run, H3N2 seasons have more hospitalizations and more deaths than H1N1 seasons. (That’s why the H1N1 pandemic had a lot of cases but not a lot of death, relatively speaking. It was still pretty bad, though.)
If you feel up to it, go check out some past seasons’ flu reports and see how some seasons compare to others.
Theoretically, you can get sick with the flu up to five times this winter. Twice with type A (H3N2), twice with type B, and once with Type A (H1N1). This is why people who get the flu vaccine report getting the flu in the same season… This and the fact that influenza vaccine technology is outdated. So go get your flu vaccine and give yourself the best shot to avoid four of the five strains about to hit us.
Don’t say I didn’t warn you.
PS: You can’t blame Mexican immigrants for this one. It was clearly the Swiss. So much for being neutral.
René F. Najera, DrPH
I'm a Doctor of Public Health, having studied at the Johns Hopkins University Bloomberg School of Public Health.
All opinions are my own and in no way represent anyone else or any of the organizations for which I work.
About History of Vaccines: I am the editor of the History of Vaccines site, a project of the College of Physicians of Philadelphia. Please read the About page on the site for more information.
About Epidemiological: I am the sole contributor to Epidemiological, my personal blog to discuss all sorts of issues. It also has an About page you should check out.