Sean O’Leary, M.D., M.P.H., who leads Colorado Chooses Vaccines, responded to the recent federal proposal to modify the U.S. childhood vaccine schedule. On January 5, Health and Human Services Secretary Robert F. Kennedy Jr. announced a plan to align the American vaccination timetable with that of Denmark.
O’Leary expressed concern about this shift, stating: “Today, Health and Human Services Secretary Robert F. Kennedy Jr. announced plans to alter the U.S. childhood vaccine schedule to align with Denmark’s. This will result in fewer recommended vaccines and other changes that will expose more U.S. children to risks from vaccine-preventable diseases.”
He further argued against delaying or skipping vaccines: “There is no evidence that skipping or delaying certain vaccines would benefit U.S. children, and no scientific reason to believe Denmark’s recommendations are safer. When a child goes without recommended immunizations, they are vulnerable to preventable diseases — some of which can be severe, life-threatening, or have lifelong consequences. Measles, whooping cough, and influenza outbreaks demonstrate the risks.”
O’Leary noted key differences between countries: “U.S. parents shouldn’t wholesale follow another country’s immunization recommendations. Different countries face different disease risks, have different health systems, offer different vaccines, and have varying schedules for childhood health visits. Those differences matter because vaccine schedules are designed not in isolation, but as part of a broader system of care. You can’t copy/paste public health.”
He emphasized that expert groups base their decisions on local data: “The expert groups that make recommendations in Denmark do so based on their country’s data, disease patterns, and health infrastructure — just as we do here in the U.S. If changes to our schedule are needed — and over the years, we have made updates when the evidence supported it — they should come from careful scientific review. That process is deliberate by design, because the stakes for children’s health are high.”
According to O’Leary: “The U.S. childhood vaccine schedule protects children from serious and sometimes deadly diseases. Every vaccine, and every recommended dose, is timed to work best with a child’s developing immune system and to provide protection when children are most at risk. The vaccination program in the United States is incredibly successful, preventing millions of illnesses, hospitalizations, deaths, and disabilities—along with avoided financial burdens, missed work and school, and caregiver strain.”
He addressed concerns about conflicting information: “Parents are hearing a lot of information right now — much of it confusing and misleading. Our role as physicians is to cut through that noise and share what the science actually shows, so families can make informed decisions with confidence. That’s why it’s so important that any discussion about the U.S. childhood vaccine schedule be grounded in evidence, transparency, and established scientific processes — not comparisons that overlook critical differences between countries or health systems.”
O’Leary concluded by supporting existing guidance: “The American Academy of Pediatrics has published its recommended vaccine schedule for many years, and it remains the trusted standard for keeping children healthy. Following the schedule on time remains the best way to ensure children receive the strongest possible protection. We will continue to publish our schedule, working with our partners across medicine and public health to ensure that parents have credible, science-backed vaccine recommendations they can trust.”
