If I wrote the book on public health I would insist on a subtitle. Here’s how it would read:
Public Health: IT’S NOT ABOUT YOU
I’m punting to the expertise of Aaron Carroll and his timely Upshot article this week. I myself, a yearly getter of the flu shot, have the flu. AND I WOULD GET THAT FLU SHOT AGAIN. Because, of course, it is not about me. And sure the flu I have is possibly less virulent than it could have been and I haven’t needed to tap the resources of any health care facility so my only cost has been reduced personal productivity (I’ve met writing deadlines but my apartment is disgusting and hair is dry shampoo). But even assuming that my flu shot did nothing to make my personal experience of flu season better, I’d still get one.
First, a statistical concept used to evaluate the efficacy of an intervention or treatment: N.N.T. or number needed to treat. Surgery is the easiest example to cite to explain it. In an appendectomy, N.N.T. is always 1. One surgery, 1 removed appendix. Unless something really weird is going on.
If everyone that got the flu shot was guaranteed to not contract the flu, then flu shot N.N.T. would be 1. One shot equals one protected patient. But the flu shot was never planned as a N.N.T.=1 type of disease prevention. The flu is too wily, too quick to mutate. Flu shots are here to reduce the disease burden in our overall population. Less infections mean less contagion, lower overall cases mean demand on public health resources is manageable, people that do get sick have better access to the care they need, and ultimately less morbidity and mortality (illness and death) result.
According to Dr. Carroll’s article, this year the flu shot’s N.N.T. is 77. For every 77 people that get the flu shot, 1 will avoid what would have been an flu infection. Considering the cost of the flu vaccine (literally zero dollars if you have any sort of insurance which legally ethically and morally you should but that is another conversation) is five minutes at CVS plus mild soreness for a day…I like to imagine my group of 77 responsible flu shot getting citizens saved a baby this flu season. Maybe that 2 week old baby I saw at the thrift store last month and wanted to scream “FOR ALL THAT IS GOOD AND HOLY GET THAT CHILD OUT OF THIS HUMAN VIRUS SOUP.”
So there’s the lesson for the day. But read The Upshot, Dr. Carroll tells it in true doctor-professor speak, and continues to explain the important role of cost/benefit in the vaccine:
Let’s say that this year’s flu vaccine is even worse than we think. Maybe the absolute risk reduction will be as low as 1 percentage point, making the N.N.T. 100. That’s still not that bad. Even at an N.N.T. of 100, for every 100 people who get a flu shot, one fewer will get the flu. That’s a pretty low N.N.T. compared with many other treatments that health experts recommend every day.