Earlier this year, the . Under an overhaul spearheaded by US Health Secretary Robert F. Kennedy Jr., the number of diseases for which vaccines are universally recommended dropped from 17 to 11. Vaccines for polio and measles remain on the list, but others鈥攍ike hepatitis A, hepatitis B, and Covid-19鈥攁re now recommended based on risk or 鈥渟hared clinical decision-making鈥� between doctors and parents.
President Donald Trump praised the move as 鈥溾��, while the American Academy of Pediatrics called it 鈥�,鈥� warning it would erode confidence in immunisation.
It seems it already has. As of late February, the , six times higher than what was once typical for an entire year. In 2025, the US reported nearly 2,300 cases, the highest annual total since 1991. Three people died, all unvaccinated.
This year, about . Large outbreaks have spread across multiple states, including nearly 1,000 cases concentrated in one region of South Carolina where vaccination rates are particularly low. Measles, declared eliminated in the United States in 2000, is once again circulating in under-immunised communities.
This situation has reminded me of a case study recently taught in in a class of mine, that aimed to dismantle the alluring promise that 鈥渓ess is more鈥� when it comes to medicine. Allow me to explain.
Tuberculosis (TB) disease develops when latent TB infection progresses to active illness. Treating infection before it advances is one of the most effective ways to prevent suffering and transmission. In the early 1990s, the only approved treatment for latent TB infection was nine months of daily isoniazid. It worked, but it was long. About 2% of patients stopped treatment because of hepatotoxicity, and only around 60% completed the full nine-month course.
Nine months is a hard sell in any decade. Researchers began searching for something shorter, and the eventual proposed solution was a two-month regimen of daily rifampicin and pyrazinamide: 2RZ. Faster treatment, the thinking went, would mean better adherence.
Two non-inferiority trials tested the idea. The enrolled 1,600 people living with HIV. Completion rates were higher with 2RZ: 80% compared to 69% with standard isoniazid therapy. Effectiveness in preventing TB appeared identical. However, 10% of participants on the new regimen discontinued because of safety complications, compared with 6% on the standard therapy.
A included 600 participants without HIV. Here, the adherence advantage nearly vanished: 61% completion with 2RZ versus 57% with isoniazid. Safety differences persisted. 11% of participants on the new regimen stopped because of adverse events, compared to just 3% on the older regimen.
In other words, the new option was shorter, but not dramatically more effective at keeping people on therapy and consistently associated with higher rates of harm.
Despite these signals, the Centers for Disease Control and Prevention (CDC) recommended 2RZ for treatment of latent TB infection in 2000.
The consequences were swift. In April 2001, the the first case of fatal hepatitis linked to the regimen. By August, five deaths had been documented. By September 2002, eight total deaths had been associated with 2RZ. The treatment is no longer recommended for anyone.
The early trials had not concealed these risks. But the appeal of a shorter, seemingly more efficient regimen carried more weight in CDC鈥檚 final decision.
The tuberculosis case study and today鈥檚 vaccine debate are not identical, but they do share familial similarities. Both reveal how high the stakes are when we recalibrate public health policy, whether by adding something new or taking something away. It鈥檚 a lesson worth remembering that in medicine, faster is not inherently better, and less is not inherently safer. Sometimes the right answer is the slower one.
It鈥檚 good to remind ourselves often that safety figures in the clinical trials we read are not just numbers on a page. They are people. And when we move too quickly, the consequences are not theoretical, they are counted in human lives.
Sophie Tseng Pellar recently graduated from 91黑料网 with a Bachelor of Science (BSc) degree in the physiology program. She is continuing her graduate studies in the surgical and interventional sciences program at 91黑料网. Her research interests include exercise physiology, biomechanics and sports nutrition.
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