As the nation experiences one of the worst flu seasons in years, thousands of Americans have already died from influenza or pneumonia (the viruses can work in tandem), according to the U.S. Centers for Disease Control and Prevention. Though the season peaked in February, the CDC recently warned that we should prepare for a second wave of cases to hit before we emerge from the season entirely. Now, it appears more than 50,000 could die from the flu before the season ends.

Perhaps most troubling is that this year marks a century since the deadliest viral outbreak in human history, which claimed the lives of 670,000 American men, women and children and as many as 50 to 100 million people worldwide. Among the lessons medical researchers gleaned from the catastrophic event is the critical importance of getting vaccinated.

It’s a lesson that much of the public continues to ignore, even as our scientific understanding of communicable diseases continues to grow.

Three factors contribute to the severity of a flu season: 1) the virulence of the flu strain that dominates in a given season, 2) the efficacy of the flu vaccine, and 3) the vaccination coverage rates. The strain in this flu season, H3N2, is particularly nasty. It’s similar to the H1N1 strain that set off the 1918 influenza pandemic, and it has resulted in high rates of death, particularly among the elderly.

Researchers have struggled to create effective vaccines for the H3N2 strain; this year’s flu vaccine is only about 36 percent effective at protecting against the virus, compared to an average of 45 percent over the past seven years. Nonetheless, it does provide some protection, and the unvaccinated are hit much harder without it. Earlier this year, a healthy young man from Pittsburgh did not get vaccinated and died soon after getting the flu. While low vaccine efficacy means that those who get vaccinated can still contract the flu, it remains common sense and good civic behavior to get vaccinated. As a result of herd immunity, even low efficacy vaccines are enough to curb a pandemic from happening if vaccination rates are high.

Flu vaccines did not exist during the pandemic of 1918, which is why it was so deadly. Yet year after year few Americans bother to get vaccinated. In economic terms, the herd immunity benefits of vaccination are a “public good.” If I am vaccinated, I cannot exclude anyone from the herd immunity that I now offer. Similarly, someone enjoying my herd immunity does not diminish someone else’s ability to enjoy my herd immunity.

What typically happens when a public good like the flu vaccine is available is that many, perhaps most, people underinvest. They free-ride off other people who get the vaccine. If too many people opt out of vaccination, communities become vulnerable to flu epidemics. According to the CDC, only 38 percent of the population chose to get vaccinated as of November 2017. Low rates of vaccination are particularly dangerous for children and the elderly, who are especially susceptible to influenza.

As individuals, we have very little control over the strain of the flu that emerges in a given year, or the efficacy of a vaccine, but we do have complete control over whether we get vaccinated. The public’s response to a bad flu outbreak or to low vaccine efficacy should be an increase in flu vaccinations, not a decrease.

Since the 1918 flu pandemic, researchers have worked hard to develop vaccines that prevent similar pandemics. We, as the public, now need to do our part and take the responsibility to get a flu vaccine more seriously; doing so is not only a personal choice but one that has real benefits for our entire community.

The population in 1918 had no alternative but to suffer. Let’s not allow their tragedy to fade without serving as a stark reminder that we have a choice that can limit the damage