Here’s a quick rundown of the 2019 flu surveillance data. I do one of these each year to see if my family should get the vaccine and if so which one. My usual guidelines are: a) skip every other year if the subtypes are the same as last year’s vaccine, b) skip it if the vaccine is a total miss, and c) get it otherwise.
Last year, during the two peak weeks, influenza caused 7.7% of all deaths in the US. If you’re a Libraries-of-Congress units types of person, that’s roughly four 9/11 attacks every year attributed to this one family of viruses. Maybe that deserves some military funding, or just FDA approval for the broad-spectrum anti-flu agents already mired in years of testing. Right-to-try ought to be expanded to any disease with such a massive body count.
TL;DR – despite possible reduced effectiveness, get the regular vaccine this year. Here’s why:
The good news is the FDA has specified all regular-dose vaccines are to be quadravalent (4-strain) this year. This is excellent news as many people have died over the past several years because the FDA recommended trivalent vaccines at “free” clinics and buying a quadravalent vaccine took serious legwork. This was extreme malpractice in my opinion; after the first year the data was clear. Anyway, deciding between tri- and quad- was one of the main reasons I do this every year, and I am glad to not have to do that again. In fact, the ‘extra’ quad component this year is a home-run. More on that later.
Down to the dirty details, then. There are some interesting observations in the latest CDC technical report [2]. First, the number of gene sequenced viruses is up 5-10x over last year. This is great, and a huge jump. Next, among the circulating H1N1, nearly all have evolved to subclade 6B.1A, vs. last year’s much larger percentage of clade 6B.1. Similarly, the H3N2 subtype 3C.3a increased from 12% to 81% in just a year. Interestingly, among the B/Victoria strains, now more than 85% of circulating strains have either a 2 or 3 amino-acid deletion in the HA protein, which binds the virus to a cell membrane. Most likely this is one of those quick evolutions which helps evade the human immune system (and makes a cultured-virus vaccine so difficult to stay current).
A bit of great news is that the B/Yamagata (Y3) circulating flu strain was 100% susceptible to the vaccine (B/Yamagata B/Phuket/3073/2013), which is the same as last year’s vaccine. So, even healthy people who don’t get vaccinated this year should have good coverage if they got last year’s quadravalent. As I mentioned above, this is the strain that was non-standard last year (16% of 2017-2018 circulating virus) and only in the quad. Almost everybody gets it this year! This could potentially reduce total deaths by 16% with more sane policy.
Lastly, a full 62% of tested 3C.3a samples (representing 28% of the circulating strains) did not respond well to the vaccine antigen test. The cause appears to be an HA protein mutation related to the eggs they were cultured in. Here’s what I don’t know (please comment if you do): will the flu shots cultured in eggs be less effective because of it? Are there any cell-cultured vaccines available on the market and are they the standard “free flu shot”? The way I’m reading this, the H3N2 (3C.3a1) A/Singapore portion of the vaccine may have very low effectiveness. The only silver lining is that this is at 7% of the current strains. It could well become more dominant if it can run rampant even among vaccinated members of the population. This may lead to discontinuance of egg-cultured flu vaccines in the future, but I don’t think anybody was sounding the alarm bells about this possibility – it seems like quite a surprise, though entirely plausible in retrospect.
Besides the virology data, I also learned one more interesting factoid: apparently the CDC has a small army of ferrets, whose job it is to fight the flu for antigenic sensitivity testing. These ferrets are probably having quite a bad time, but the information they provide could very well save thousands of human lives. However, for people who take a principled stand against animal testing – you should probably not get the flu vaccine, as its composition is determined to a significant degree based on animal testing. I do implore you to let your kids make that decision for themselves when they turn eighteen, though.
Bonus section: Antivirals. Treating flu with antivirals depends on catching it super-early, and getting immediate treatment for maximum effectiveness. It’s probably a waste of money, otherwise, in most cases, but if my life depended on it, I’d ask for a cocktail of the endonuclease inhibitor baloxavir (Xofluza) and the neuraminidase inhibitor zanamivir.
Again in 2019, as of right now, New England is showing minimal activity but the Mid-Atlantic is picking up steam. Act accordingly.
[1] https://www.cdc.gov/flu/season/faq-flu-season-2019-2020.htm?CDC_AA_refVal=https%3A%2F%2Fwww.cdc.gov%2Fflu%2Fseason%2Fflu-season-2019-2020.htm
[2] https://www.cdc.gov/mmwr/volumes/68/wr/mm6824a3.htm?s_cid=mm6824a3_w
