Hello and welcome to Healthbeat's weekly report on stories shaping public health in the United States.

I am Dr. Jay K. Varma, a physician, epidemiologist, and public health expert currently serving as chief medical officer at Fedcap, a global nonprofit focused on economic mobility and well-being for vulnerable communities. Views expressed here are my own.

I often write about what's not working in public health. This week, I want to focus on a few recent studies that show what is working in public health — from reducing tobacco use to preventing one of the world's deadliest killers — and put it in the context of how we think about interventions to avert illness and death in large populations.

What interventions work best in public health?

When we are trying to improve the health of a population, we try to choose interventions that benefit the largest number of people for the longest amount of time with the least amount of effort required on a daily basis. 

In a framework first promulgated by former Centers for Disease Control and Prevention Director Tom Frieden, the most effective interventions address the socioeconomic factors that have the largest impact on health and longevity, such as poverty, education, and housing. The second most effective are interventions that change the default context for how people make healthy decisions, e.g., clean water, safe food, smoke-free places, and seatbelt mandates. These work because the healthy choice becomes automatic. 

Third most effective are long-lasting protective interventions, such as vaccines or colonoscopies, that confer durable protection from a single encounter with the health system. Fourth most effective are ongoing clinical interventions, such as medications to treat blood pressure or HIV. And, fifth, the least effective in a population, is counseling and education about health: telling people to eat better, exercise more, stop smoking. Trying to talk one person into changing their behavior is hard. Trying to talk millions of people into changing their behavior is even harder and often fails.

Even though we have a hierarchy of what works best in public health, each of these types of interventions has value, as shown by multiple recent studies.

Changing the context: Tobacco use at a historic low

Cigarette smoking just fell to its lowest recorded level in U.S. history. A study published this month in NEJM Evidence, using 2023 and 2024 National Health Interview Survey data, found that cigarette smoking among U.S. adults dropped from 10.8% to 9.9%, the first time it has ever reached single digits. Tobacco kills roughly 480,000 Americans each year. If this trajectory holds, the United States could meet the Healthy People 2030 target of 6.1% before the decade ends.

What drove this decline? While many people probably think it was because of better education about smoking’s harms, most of the gains in tobacco control came from years of investment in changing the default context: High tobacco taxes and comprehensive smoke-free laws that made smoking expensive to start and disruptive to continue. 

Unfortunately, this progress is not guaranteed to sustain. The current administration has had virtually nothing to say about tobacco and even eliminated the CDC's Office on Smoking and Health. Congress is trying to restore it, and so I remain hopeful that the United States will continue to drive tobacco use down.

Worth noting is that e-cigarette use has not declined and sits at 7% among adults, with rates among young adults running significantly higher than cigarette smoking. And we still do not know what the long-term consequences of vaping will be.

Long-lasting protective interventions: Flu vaccine still worth getting

Vaccines are among the most cost-effective tools in all of public health. Some, like measles or polio vaccines, are delivered in the first few years of life and protect people for decades. Others, like flu vaccines, work differently: Because the virus mutates rapidly, the vaccine has to be redesigned each year, and protection is partial rather than complete.

The CDC just published data showing both the benefits and challenges of getting a flu shot every year. The dominant circulating strain this year (influenza A[H3N2] subclade K) emerged after this season's flu vaccine was already selected, a mismatch that predictably lowered effectiveness. Among children and adolescents, vaccine effectiveness against outpatient visits ranged from 38% to 41% and, among adults, 22% to 34%.

While those numbers are much lower than I would like, one of the most important axioms of public health is that a small number multiplied by a very big number is a big number. Even partial protection against a disease that infects tens of millions of people means that tens of thousands of people did not end up in a hospital from the flu. For example, during the 2022-23 flu season, when overall flu vaccine effectiveness was also just 30%, flu vaccines still prevented an estimated 71,000 hospitalizations and 4,300 deaths in the United States. 

Clinical interventions: DoxyPEP and tuberculosis

While medical care is often seen as the most important part of health, it is often less effective than other public health interventions, because it requires accessing a clinic, getting the right diagnosis, and maintaining adherence to treatment. Public health's primary role in medical care is making sure that people who need it most complete these steps.

Syphilis rates in the United States have been rising sharply for a decade. In 2023, King County, Washington began actively promoting doxyPEP: prescribing a single dose of the antibiotic doxycycline that patients can take within 72 hours of unprotected sex to prevent bacterial sexually transmitted infections. The intervention is recommended for men who have sex with men and transgender women who have sex with men, the populations at highest risk.

A study published last week in Clinical Infectious Diseases assessed the two years after doxyPEP was introduced in King County. Syphilis cases fell by 52.3% overall, an absolute reduction of more than 3,000 cases. Cases fell among cisgender women as well, likely through an indirect effect: As transmission declined in high-risk groups, it declined in their broader sexual networks, too. 

The CDC also just released its provisional tuberculosis data for 2025. Cases declined slightly from 10,395 to 10,260, a 1% drop. Cases had been increasing for four straight years, a reversal of the CDC’s long-standing progress toward eliminating domestic TB transmission. 

TB demands more from the health system than almost any other infectious disease, because it requires specialized testing and prolonged treatment. Diagnosis is often delayed, because the symptoms are burdensome but not debilitating, and most cases occur in immigrants and other groups that have limited access to high-quality medical care. Treatment requires months of strict adherence to multiple antibiotics. For this reason, most TB care is either provided directly by public health agencies or monitored closely by them. 

I am worried that the United States will not be able to sustain this decline. Much of the progress against TB elimination in the United States has come from sustained investment in domestic public health services and in global TB control, both of which have been cut dramatically in the past year. 

What these findings have in common

Tobacco control, flu vaccination, doxyPEP, and TB treatment sit at different levels of the public health hierarchy of interventions, but they share a common feature: None of them happened spontaneously. They required sustained government investment, functioning public health agencies, and the political will to keep at it year after year even when the gains seem small and the benefits invisible to the naked eye. 

ICYMI

Here’s a recap of the latest reporting from Healthbeat:

• Measles: Michigan outbreak shows high cost of stopping even a small number of infections from spreading

• Fresh water: Iran war threatens systems that keep drinking water flowing in the Gulf

• Genome sequencing: U.S. scientists sequence 1,000 genomes from measles

Until next week,

Jay