The most dangerous misconceptions about public health

In the year 2024, nobody in New York City died of cholera. But from the 1830s to 1850s, New York City’s mortality rate doubled amid a string of local cholera epidemics. 

Cholera can cause diarrhea so severe and dehydrating that it proves fatal within hours. An infected person might lose a quart of fluid and critical minerals from their body every 60 minutes, until the resulting electrolyte imbalance leads to shock, kidney failure, coma, and death. In the 19th century, back-to-back-to-back cholera pandemics wracked the globe. People became ill en masse, especially in cities, dying miserable deaths by the thousands. 

Yet in the present, there hasn’t been an outbreak of the bacterial disease in the United States since 1911. Other diseases like typhus have also all but disappeared. 

Targeted infrastructure projects and policies explain why. Both cholera and typhus spread through water and food, which can be contaminated by feces particles from infected people and animals. By tackling the sanitation crisis that contributed to the disease, New York dramatically cut case numbers. The city constructed and then repeatedly expanded a reservoir and aqueduct system to store and transport fresh drinking water from upstate. Seventy miles of sewers were laid in New York between 1850 and 1855, keeping untreated waste out of the street. Lawmakers restricted livestock in tenements and ordered manure to be cleaned up from yards and vacant lots. “In the years 1880 to 1920, we literally transformed the health environment,” says David Rosner, a professor of history and public health at Columbia University, and author of the book, Building the Worlds That Kill Us. “By the 1920s, we already began to notice that the infectious diseases of the 19th century were waning–that infections were suddenly fading away,” he says, in a shining example of the value of public health interventions. “We take it for granted today,” he adds.

Public health encompasses any and all actions at the societal and governmental level to ensure community health and safety. It is focused on preventing sickness and harm before it happens. Everything from seat belts, driver’s licenses, laws against drunk driving, vehicle design, and urban planning to municipal water testing and treatment, hand washing, flush toilets, and food recalls fall under public health’s vast umbrella, says Georges Benjamin, a physician, career public health official, and executive director of the American Public Health Association.

But there’s a difficulty inherent in public health: when it’s operating well, it’s invisible. “What public health does is very silent. We’re behind the scenes. When we do our best work, nothing happens,” Benjamin tells Popular Science. Most interventions go unnoticed and unappreciated. 

In lieu of awareness, doubt and insidious propaganda can seep in. Opposition to public health interventions isn’t new. For every policy and technology–there’s always been a hypervocal contingent against the advance. But in recent years–and especially in the aftermath of Covid-19 lockdowns and restrictions–many long-standing efforts have come under strengthened political attack in the U.S.. Vaccination, dairy pasteurization, and water fluoridation are all facing renewed scrutiny, largely as the result of mis- and disinformation. Trust in science and health officials has declined. So have childhood vaccination rates–falling from 95% among kindergarten children pre-pandemic, to 93% between 2023 and 2024, according to data from the CDC. 

Popular Science spoke with three public health experts to better understand why. They explained how they think about the work of public health, and debunked some of the most commonly held misconceptions they encounter about their field. As the start of the new presidential administration brings chaos and uncertainty to public programs and health institutions, here’s what the experts want you to know.

[ Related: How to talk to your ‘skeptic’ family about science misinformation ] 

Public health doesn’t eliminate risk. It reduces it.

The flu vaccine does not guarantee that you won’t get sick with the flu. Water treatment infrastructure does not eliminate all water borne illness. A buckled seat belt and airbags don’t prevent all traffic collision deaths. Public health interventions cannot and do not eliminate all risk, says Rupali Limaye, an associate professor of global and community health at George Mason University.

“The goal of public health for most of these interventions is to reduce risk and severity,” says Limaye. Ideally, people should not expect absolute protection, and should not interpret breakthrough infections or accidents as evidence of failure, but rather know that public health works to minimize the chances of the worst outcomes.

The flu vaccine and most other vaccines lower your individual risk of infection, severe disease, hospitalization, and death. It also helps reduce risk for your close contacts and loved ones who may be vulnerable to disease complications. The more people get vaccinated, the more risk falls for the population as a whole, because diseases encounter more dead ends and infections spread less readily.

Often, there is a small risk associated with an intervention itself. Seatbelts, for instance, can increase the risk of a clavicle fracture in the event of a collision. But at the same time, they prevent more serious injuries and save thousands of lives each year. The risk vs. reward is assessed through careful tests with crash test dummies, and long-term data collection and analysis.

The same is true of vaccines, which carry the potential for side effects. Vaccines, as with all pharmaceuticals, go through years of safety and efficacy testing. This includes multiple animal and human research trials, each overseen by an independent Data and Safety Monitoring Board (DMSB) made up of scientists and health experts who aren’t affiliated with the trial or the company conducting it. Then, the Food and Drug Administration conducts a separate regulatory review before any vaccine can be approved. In all of this, the benefits have to far outweigh any risks before a vaccine moves on to the next step, says Limaye. “We’re usually talking decades of work,” she adds.

In extreme instances, vaccine approval can move more quickly, as in 2021 when the first Covid-19 vaccines received approval under emergency authorization. But still, Limaye says years and years of work had gone into studying mRNA vaccines preceding the pandemic, there were still independent review boards, and there was continual data evaluation throughout to track outcomes and update guidelines about who should be vaccinated. Public health is a balancing act between risk and benefit, Limaye says. An intervention isn’t generally put into effect unless “for the overwhelming majority of people, the benefits outweigh the risks.” 

Science isn’t static. Guidelines change with new knowledge.

If a public health intervention shifts through time or a guideline changes, it’s not because the experts in charge are untrustworthy or trying to trick you. “Facts are facts, but science is an evolving process of evaluating and re-evaluating what we know,” says Benjamin. 

You probably remember that, during the Covid-19 pandemic, the guidelines around masks changed. Initially, masks weren’t recommended for most people and the CDC actually urged the public to forgo masks to conserve supplies for healthcare workers. In part, this was based on past knowledge of related viruses, says Benjamin. Covid-19 is caused by SARS-CoV-2, a virus in the SARS family. In prior SARS virus outbreaks, most people were not infectious until they were symptomatic. With SARS-CoV-2, that changed. As a growing body of research supported that asymptomatic people could spread Covid-19, and that the virus was airborne, the CDC began recommending masks.

“It turns out we were wrong, and that does happen.” Benjamin says. “We were trying to be judicious [and avoid pushback] in our initial recommendations, but I don’t think we explained the change adequately.”  

If a public health agency changes a guidance, it can be easy to assume ineptitude–but it would be more accurate to assume that updated advice means updated information. It almost certainly means someone has worked to understand the problem better. 

When things go right, they don’t go viral. 

If you’re on social media, chances are you’ve come across someone sharing a negative experience about a vaccine, medication, healthcare provider, or health agency. Dramaticstories of supposed vaccine injury or corrupt systems frequently go viral. But just because you see or hear about it doesn’t mean it’s true and or representative. Sixty-five percent of anti-vaccine misinformation circulating online in 2021 could be traced back to just a dozen social media influencers, according to an analysis from the Center for Countering Digital Hate. Part of what makes their content so shareable is that it’s shocking and sensational.

What you hear about far less often is the status quo. “It’s hard to sell a story where nothing happened,” says Limaye. “It’s hard to say, ‘I got a vaccine and because of that I didn’t deal with an infectious disease’,” she explains. Yet that’s the overwhelming majority of peoples’ experiences. “I’m not going to go viral for saying, ‘I got the shot and I’m fine,’” Limaye notes.  

Public health decisions are based on population-level data. Yet anecdotes and narrative can hold outsized sway over public opinion, particularly on emotionally charged issues. To stay in the game, Limaye believes public health experts will have to get creative, and embrace storytelling. “We have a lot to learn.” In the meantime, consider thinking about your health and safety the way an epidemiologist or city planner might. A story about an unexpected disease cure or an especially dangerous intersection could be a reason to investigate and collect data– but it’s not a basis for ignoring current advice. 

Public health is not a power grab or a money maker. 

The vast majority of pharmaceutical companies are for-profit entities but, compared with other products, vaccines are not the money-making venture they might seem, says Limaye. Vaccines account for a relatively small share of pharma company profits, at less than 10 percent of all sales. Drugs that people have to take on a daily basis, like cholesterol medication, are much bigger sources of profit. The three doses of the vaccine for hepatitis B, which are recommended for children, cost under $100. In comparison, the lifelong treatment for Hepatitis B is thousands of dollars each year. Pharma companies can make a lot more money off of you if you’re not vaccinated. 

Your doctor’s office might even be losing money through vaccines. A provider has to purchase the vaccine stock, properly store the doses, plus staff an office. The reimbursement insurers offer for administering a vaccine is usually not enough to offset those costs. Nearly a quarter of family medicine doctors reported no longer purchasing vaccines because of financial concerns, according to a 2017 study in the journal Academic Pediatrics. 

As a rule, public health measures are far cheaper for you than the alternative of getting sick or injured and having to pay for treatment after the fact. If we still routinely became sick from our water supply, we’d be collectively spending much more on healthcare. If we didn’t have traffic lights or drunk driving restrictions, you can bet that emergency services would be a far bigger business. 

In contrast, people who build careers out of railing against public health measures often do have a financial incentive. Robert F. Kennedy Jr., for instance, is poised to make money off of vaccine injury lawsuits that he’s maintaining a financial stake in–even as he faces confirmation to lead Health and Human Services and regulate the makers of those vaccines. 

Aside from money, some can get caught up believing that public health is about control and power. And it’s true that abiding by public health guidelines and policies can involve sacrificing a degree of personal freedom for community safety and benefit. You can face criminal charges for driving while intoxicated or penalties for driving without a license, for instance. “There’s a trade-off there,” says Benjamin. But those laws are established through a legal process, underpinned by elected legislators. It’s a democratic process, he says. “We’re not evil authoritarians,” says Benjamin. Plus “most of what we do is by recommendation.” Often, people can opt out.

“Public health workers go into the field, not because they’re going to get rich or get political power, they’re invisible.” says Rosner. “They went into it because they wanted to help. They want to make a better world.” 

Threats don’t disappear. Interventions shouldn’t either. 

Once a public health measure is in place, it can be tempting to assume that–at some point–the work will be done and the effort can end. But most public health endeavors require continual investment and upkeep.

There is no point at which we can stop maintaining our waste water infrastructure and still expect it to protect us from getting sick. A motorcycle helmet can only prevent injury if you keep putting it on your head. 

Smallpox is the only human disease that’s been globally eradicated through a vaccination campaign. It no longer occurs naturally. But every other illness that we have vaccines for is capable of making a resurgence in the U.S.. Just a 5% dip in vaccine uptick could lead to a major measles outbreak. We’ve already seen that dynamic play out in pockets across the U.S. in recent years. As vaccine hesitancy has risen, so too have measles cases. A 2019-2020 measles outbreak in Samoa, following the suspension of vaccines, resulted in 83 deaths, mostly of young children. In 2022, the U.S. saw its first evidence of circulating polio in thirty years. 

If politicians continue to sow doubts about vaccination, or even take steps to restrict vaccine access, then the trend of re-emerging disease will continue. “I think we’re going to see a lot more infectious disease that’s going to affect everything from school attendance to sporting events,” says Limaye. 

Ultimately, the outcome of increased disease is increased death. More than 40% of children died before their fifth birthday in the U.S. in 1800. We don’t need any sort of natural experiment to demonstrate what happens when public health measures dissolve. Instead, we have centuries of human history to inform what life was like. It involved a lot more deadly diarrhea.