Five Things You Probably Didn’t Know About the Flu Shot

Email a Friend
Flu shots at the K-Mart Pharmacy in Penn Station.

While researching this week’s episode of Only Human, I learned a lot about the flu vaccine. Here are my top five takeaways:

  • Every year, the flu shot is a little bit of an experiment. In the next couple of weeks, a team of physicians will get together and vote on what should go inside it. In this article from a couple of years back, one of those doctors acknowledged “the virus is smarter than we are at this point. I don’t know of any disease that plagues us more. It’s very, very frustrating and a very inexact science. . . . We do it with varying luck, and I think the luck is mostly the virus’s whim.”
  • The “flu shot” isn’t just one thing. Every year there are a bunch of different versions of the flu vaccine: some inoculate you against three strains (trivalent); others inoculate you against four (quadrivalent). Some versions are more effective than others, and last year the CDC had to un-recommend a flu vaccine called FluMist (a nasal spray), because it was 0% effective. The vaccine we’re talking about this week, Pandemrix, was only available in 2009-2010, the year of the swine flu pandemic - it was monovalent, containing only one strain, the H1N1 virus.
  • A “universal” flu vaccine is the “holy grail” of flu vaccines. But it’s at least a decade away. You have to keep getting the flu vaccine again and again because the virus “drifts”: it shape shifts just enough each year to totally confuse your immune system. A doctor in New York is hard at work on a vaccine that could last for years, but getting it to clinical trials has been a challenge. (It looks promising when it’s tested… in ferrets.) You can hear a story I did a couple months back about the quest for the universal shot by clicking here.  
  • Things that might be in your flu vaccine: shark liver oil, cow bile, egg protein. And all of this stuff is totally safe. It's just weird. The shark liver oil "boosts" a vaccine's effectiveness; the cow bile helps clean the viral proteins. The egg protein is there because the flu shot is grown inside chicken eggs. In the US, flu vaccine is made and packaged in Pennsylvania - which, as a state, is the third-largest egg producer in the country.
  • There’s a reason you’ve never heard this week’s story before. This is a really thoughtful piece from Vox about why science journalists have a hard time talking about vaccine side effects — and why we need to do better.

Bottom line, the flu shot — like all shots — is safe and effective. But newer vaccines may have side effects that become apparent only after millions of people try them out.