So, really, this is sort of like talking about how seat belts may cause redness or irritation on bare skin and, in rare cases, can cause internal bleeding and organ damage during a serious car accident. If you focus on those risks, wearing a seat belt sounds like a bad idea. Why take a chance? But the value of seat belts becomes obvious when you shift your focus to the danger of going without a device that saves tens of thousands of lives every year.
Likewise, when weighing the risks of getting a flu shot, you have to consider the much more relevant risks of not getting vaccinated. We get used to health risks—such as deaths from car accidents, heart disease, gun violence, and influenza—as they lose their novelty and start to take them for granted, but that doesn’t make them any less dangerous. Somewhere between 10,000 and 60,000 Americans die of the flu each year. Combine that with the effects of so much illness and missed work, and the virus’s annual impact on the U.S. economy is about $90 billion.
This brings us to the upside: If everyone got a flu shot, we could bring those numbers down to about zero. Vaccination is a measure that we undertake to remove ourselves from the pool of susceptible people who can become vectors of disease. You have a great opportunity to do an essentially risk-free thing to play your part in saving thousands of lives. And there’s really no opting out. Whatever you choose, it affects everyone. It’s a personal decision in the same way that driving on the sidewalk is a personal decision.
This is true of getting any vaccine, but especially flu shots, because of the nature of the virus. Influenza mutates so rapidly that each year’s vaccines are based on modeling predictions about which strains will spread most widely. Some years those models work pretty well, and other years they don’t. Even in a good modeling year, a flu shot offers only partial immunity: Some people who get the shot will still be susceptible to the flu. The imperfection means it’s especially important that everyone gets vaccinated to achieve some degree of herd immunity. When you have a more reliably effective vaccine, you can get to herd immunity with a smaller percentage of the population being vaccinated. But with the flu vaccine, we always need to aim for 100 percent participation. Each year, about half of Americans get vaccinated.
A partially effective vaccine has one other important effect: It can make the disease milder even if it doesn’t prevent an infection. That means a lower likelihood of going to the hospital and fewer days of being sick. Even if that doesn’t matter to you personally—maybe you have unlimited sick days, or maybe you like being sick (I don’t know)—a shorter course of disease means you’re less likely to infect other people. That’s ultimately what vaccination is about.