On April 22, scientists will march on Washington, D.C. in support of empiricism, data and fact-based policy making. The young Trump administration has already shown itself to be at best skeptical, and at worse hostile, to these principles. From its flirtation with climate change denial to its dim view of the proven effectiveness of vaccines, this presidency has worried the scientific community, galvanizing political action.

The choice to engage with politics is one that many of us scientists do not take lightly. Historically, science prided itself on avoiding the appearance of partisanship, letting the facts speak for themselves. While this may have been effective in earlier days, our present moment clearly demands a new approach. In public health, we seek to influence the social, economic, and environmental conditions that shape the wellbeing of populations. This makes us perhaps unique among scientific disciplines, in that the success of our work depends on robust political engagement. As the larger scientific community begins to find its feet in the world of politics, I would like to suggest four lessons we could all learn from the history of public health, to promote progress in our new civic era.

1. Changing science takes time. Changing attitudes takes even longer.

In the 19th century, a bacterial uterine infection called puerperal, or “childbed,” fever was a common postpartum killer. In the 1840s, Ignaz Semmelweis, a Hungarian obstetrician, began collecting data to find out why so many women in the Vienna General Hospital were dying of this disease. Between the two maternity wards in the hospital, one staffed by midwives and the other by doctors, he noticed that the death rate was significantly higher in the latter. He hypothesized that there was some kind of “morbid poison” on the doctors’ hands, which they carried from their work in the autopsy room to their work in the maternity ward. He began requiring his staff to wash their hands with a chlorine solution, cutting the mortality rate from 18.27 percent to 1.27 percent in the wards staffed by doctors and medical students.

Despite this clear public health success, the medical community did not immediately embrace handwashing. Doctors resented the idea that they might be responsible for spreading disease. The American obstetrician Charles Meigs spoke for many when he said “Doctors are gentlemen, and gentlemen’s hands are clean.” It was not until the confirmation of germ theory that medical sanitation practices would gain greater acceptance.

Semmelweis himself would not live to see his methods vindicatedin 1865, he died in a mental institution, a marginal figure. The moral here is that even something as seemingly self-evident as the benefits of handwashing can encounter severe pushback if it challenges an established practice or worldview. This speaks to a core truth of scientific activism: it is frequently a slow, frustrating grind. But progress, more often than not, wins out in the end. It just needs to be coupled with patience, and consistent, committed advocacy.

2. Now is a time for strange bedfellows.

Making change means building coalitions, and, sometimes, partnering with groups and individuals who may not seem at first like natural allies. One of the key public health achievements of the last century—the dramatic decline in U. S. smoking rates—offers an example of the power of these partnerships. It can be easy to forget that smoking was once ubiquitous, socially acceptable, and even considered glamorous. The glamour was not so much a product of the frequently ugly reality of smoking itself; in fact, a lot of money was spent to construct the appeal of cigarettes. Sophisticated advertising campaigns were used to link smoking with the ideals of worldliness and comfort, with celebrities lending their familiar faces to these efforts.

When the dangers of smoking became apparent, ads would even feature “doctors” touting the “health benefits” of a favored brand. Subsequent declines in smoking are the product of many factors, including greater scientific evidence about the dangers of tobacco, and policy solutions like taxation and restrictions on where smoking is permitted. It is important, however, to acknowledge the critical role of anti-smoking advertising in these public health efforts, as the same methods of persuasion once used to sell cigarettes are now used to discourage their purchase. Working with advertisers has allowed activists to reverse some of the damaging trends that the marketing field helped to create in the first place, demonstrating how fruitful such unexpected partnerships can be. As scientists mobilize, an openness to similar alliances—whether with the corporate, political, or even entertainment world—could serve their cause well.

3. Tell a story.

In today’s polarized world, it is not enough to support our arguments with evidence. We must also connect our message with the unfolding story of the society we seek to influence. The tale of vaccines in the U.S. is a case in point. Almost from the moment of their introduction to the North American continent, vaccines have been central to the story of American progress; a product of the same Enlightenment spirit that inspired the nation itself. Thomas Jefferson was an early proponent of vaccines; later, in the 20th century, the success of American vaccine development in preventing diseases like polio mapped well onto the broader narrative of the “American Century,” with the researcher Jonas Salk embodying the heroism associated with vaccine research during this period. Scientists need to reclaim this narrative to counter the voices that cast doubt on the effectiveness of vaccines. Rather than simply warning of the dangers of a world without vaccines—great as these dangers are—scientists must communicate the dynamic, affirmative story of vaccines in order to safeguard their continued use. This embrace of narrative is crucial if our data are to move hearts as well as minds.

4. Fundamentally, it is about influencing policy.

Public health has long recognized the importance of shaping political policy as an indispensable part of its mission, one that is every bit as vital as research, medical innovation, and other advances. Working proactively in the realm of policy can yield impressive results. In 1999, the Centers for Disease Control and Prevention named improvements in motor-vehicle safety as one of the top public health achievements of the 20th century. Despite the fact that Americans now travel more miles than ever before, the CDC was able to report a 90 percent decrease in annual U.S. road deaths since 1925. This decline could not have been achieved without progress at the legislative level. The introduction of seat belt laws, as well as legislation that set regulatory standards for roads and vehicles, created a framework for safer highways.

Rarely do scientists pursue their research simply for its own sake. At core, we want to make a difference. To do so effectively means working within the political system, while also applying the kind of external pressure represented by protests and marches. Going forward, the movement to advance scientific progress could look to the history of public health to see how an engaged, activist scientific class can create a better world, even in the face of challenges.