Dec 16, 2018 1 min read

I commend the Dec. 10 piece, “Countering misinformation about the flu vaccine is harder than it seems,” which is good timing for the coming flu season. I have little to add except explaining why last year flu vaccine didn’t work as well as expected with a dismal overall 36 percent efficacy, lest people would lose confidence on flu vaccine.

Last year flu vaccine was only 25 percent effective against H3N2 (a subtype of influenza A), 67 percent against H1N1 and 42 percent against influenza B. Unfortunately most of the flu (67 percent) circulated last year was H3N2, not the one the Centers for Disease Control predicted. This contributes to the overall lower efficacy.

The high prevalence and low vaccine effectiveness against A (H3N2) made the high severity 2017-18 flu season with 49 million fell ill, one million hospitalized and close to 80,000 deaths, half of them children.

Dr. Jer-Yuan Tsai

The letter writer is a physician who practices at Carmichaels Clinic in Greene County.