There’s Something Rotten In The United States

Why the Denmark Vaccine Schedule Won’t Work in the U.S.

Special thanks to Dr. Kayleen Schreiber for leading this piece and developing our interactive data visualizations (she is not on Substack)!

It’s official. CNN confirmed that the Department of Health and Human Services was planning to announce an overhaul of the U.S. childhood vaccine schedule to align it with Denmark’s, which recommends fewer vaccines (as The New York Times also reported). The announcement seems to have been pushed to 2026, reportedly to avoid conflicting with the White House’s drug pricing news. But… it is coming.

This follows President Trump’s December 5 Presidential Memorandum and an eventful meeting of the Advisory Committee on Immunization Practices (ACIP), in which Tracy Beth Høeg, newly named acting director of the FDA’s Center for Drug Evaluation and Research, gave a presentation about vaccination practices in Denmark, suggesting that the U.S. follow that country’s approach.

This alignment is dangerous and not backed by any sound data or evidence.

• The U.S. healthcare system is ranked worst among high-income nations. We can’t copy the guidebook of countries with universal healthcare without seriously bad outcomes for our most vulnerable.

• The U.S. is much larger and more diverse than European nations. Our vaccination plan must reflect that.

• The argument that our vaccination schedule is bloated, unnecessary, or not evidence-based is a smokescreen to cover an underlying ideological move away from vaccines.

No, the current schedule isn’t bloated; it’s one of the most successful public health interventions we have. Since 1994, routine childhood vaccines have prevented over 500 million illnesses, 32 million hospitalizations, and more than a million deaths.

And the predictable outcome of these actions is not theoretical: more preventable illness, more hospitalizations, more long-term complications, and more deaths—especially among infants, children with chronic conditions, and families with the least access to care. It also means more missed school days for children, more missed work for parents, and higher medical and financial strain on families.

Why Vaccine Schedules Aren’t A Simple Copy-Paste

Comparing vaccine schedules between countries is like comparing traffic laws between cities. In one city, the speed limit might be 55 MPH because the roads are wide and straight; in another, it’s 35 MPH because the streets are narrow and crowded. Both systems are designed for safety, but they depend on local conditions such as population density, infrastructure, and accident rates. If you swapped speed limits without considering all those factors, you’d create unsafe roadways and utter chaos. Similarly, vaccine schedules are tailored to each country’s disease incidence and prevalence, healthcare access, and public health priorities. Copying another country’s schedule without context doesn’t make sense.

“Fewer Diseases” Is a Talking Point, Not a Health Metric

The U.S. recommends vaccination against 18 diseases for all children. The memorandum first contrasts the U.S. with Denmark, which only recommends universal vaccination for 10 diseases. They also mention Japan (14) and Germany (15). This numerical comparison treats vaccine schedules as if they are interchangeable menus, with some having more items and some having less. The implicit message is that “more is bad.” But the number of diseases included in the schedule is not the metric that matters most to public health. More important metrics include:

• Hospitalizations prevented

• Deaths prevented

• Disabilities prevented

• Outbreaks avoided

• Healthcare costs avoided

Counting diseases is like counting different types of road hazards when evaluating how well a city keeps its citizens safe, rather than measuring actual accidents prevented and lives saved. The premise that “fewer vaccines against fewer diseases = better” only makes sense if one starts with a mistaken assumption that vaccines are inherently harmful and should be used less. Instead, we should be recognizing them as tools that prevent serious illness and death.

Below is an interactive chart that compares childhood vaccination schedules across countries, with each color representing a different vaccine-preventable disease. The x-axis shows the country, and each dot indicates a vaccine recommended for children under 18 in that country’s standard immunization schedule.

Note: This comparison includes only routine vaccinations for all children. It excludes vaccines recommended solely for high-risk groups, shared decision-making scenarios (such as COVID-19 or MenB in the U.S.), or population-specific recommendations (like those for Aboriginal populations in Australia or Indigenous/specific Canadian Provinces).

Country-Specific Considerations: Japan’s schedule includes a vaccine for Japanese Encephalitis and BCG (a vaccine against tuberculosis), which are not endemic in the U.S. For Meningococcal disease (shown in tan), hover over the dot to see which strains are covered—ACWY, B, and/or C—as these vary by country (e.g. MenB is a routine vaccine in the U.K.)

Denmark: A Cherry-Picked Comparison

The comparison to Denmark specifically is unhelpful in multiple ways: for one, if we just compare peer nations for the number of diseases vaccinated against, Denmark is the lowest country on the list, so more of a low outlier than a country that would make sense to compare to the U.S. In addition, Denmark is the smallest country on the list, with only about six million people and a land mass about the size of Maryland. And if we’re comparing peer nations, why stop at Denmark? Canada, Australia, Ireland, New Zealand, France, Italy, and Spain all have childhood schedules that look far more like the U.S. than Denmark’s. The U.S. isn’t a high outlier. Denmark is a low outlier, which is presumably why it was chosen.

The interactive chart below compares population sizes of the countries referenced in the vaccine schedule debates. Note that Denmark’s population of ~6 million is roughly the size of Maryland.

So, comparing the U.S. to Denmark starts to look like an intellectually dishonest strategy to make the U.S. schedule seem bloated by any means necessary. But the most obvious omission in the discussion is the differences in healthcare systems across countries. A recent report analyzed healthcare systems from 11 high-income countries, and the U.S. ranked the worst overall. Based on performance across five domains—access to care, care process, administrative efficiency, equity, and health care outcomes—the U.S. ranked worst in every domain except care process. You can see the overall performance scores by hovering over each country below.

In Denmark, parents are entitled to 46 weeks of paid leave. They have universal healthcare and comprehensive medical records for every person from birth to death. This contrasts with the U.S., where many mothers go to work just a few weeks after giving birth and infants are enrolled in group childcare settings much earlier. In fact, the U.S. has no federally guaranteed paid parental or sick leave. Because of healthcare costs, many moms and babies miss appointments and follow-up care after birth.

How Vaccine Schedules Are Actually Created

Vaccine schedules are created not solely from clinical trials, but rather from a combination of clinical trial data, burden-of-disease studies, well-child visit schedules, and post-vaccination surveillance. Vaccines are administered at optimal ages based on a region’s vulnerability to vaccine-preventable diseases, which may differ by region. This optimization takes into account the age at which the immune system can tolerate vaccine components, potential interference from maternal antibodies, the age when a child is most at risk for disease transmission, and logistical factors regarding when kids will have access to doctors and vaccines. And adjustments to the schedule have been made when clear evidence of risks emerges, as in 1999, when data showed a possible increased risk of intussusception (a type of bowel obstruction) in infants. CDC removed its recommendation of the rotavirus vaccine. The U.S. vaccine schedule is monitored, studied, and adjusted when relevant data comes in, but not for ideological or political purposes.

Public health decisions must also prioritize community safety and prevent the spread of disease. The proportion of the population that needs to be vaccinated to achieve herd immunity varies by disease and depends on factors such as contagiousness, population density, contact patterns, and access to health care. The arguments at the recent ACIP meetings (presented by individuals hand-picked by RFK Jr.) have focused solely on personal choice and individual perspectives, rather than balancing that with the protection of the most vulnerable.

A Case Study: Hepatitis B at Birth

Take hepatitis B virus (HBV), for example. Until a couple of weeks ago, the U.S. recommended all babies receive the hepatitis B vaccine (HepB) within 24 hours of birth. Denmark recommends it only for babies with mothers who test positive for HBV. Why the difference? In Denmark, nearly all mothers are screened for HBV during pregnancy. In the U.S., however, 12 to 18% of pregnant women don’t get tested for HBV, and only 35% of those who test positive complete the recommended follow-up care. The consequences of HBV infection are dire. Ninety percent of infants who contract HBV develop chronic infection, which can lead to cirrhosis, liver cancer, and premature death. Especially frustrating is that we have data on what happens in the U.S. when we don’t have a universal recommendation for the HepB vaccine at birth. Even when all babies born to mothers tested positive for HBV were given the vaccine, tens of thousands of babies every year ended up infected by family members or caregivers because HBV doesn’t only spread through sexual contact or drug use. Infants can get infected through microscopic blood transmitted through cuts and everyday exposures. Many adults do not know they have HBV because it can be asymptomatic. So the recommendation change takes us back to a time when babies got infected and died from a disease we know how to prevent.

HHS just awarded $1.6 million to researchers in Denmark to conduct a randomized controlled trial of the HepB birth dose in Guinea-Bissau, a country with an adult HBV prevalence of 18.7% (compared to 0.3% in the U.S.). While the full protocol hasn’t been publicly released, available information suggests the study will compare infants who receive the vaccine at birth with those who receive it around 6 weeks—Guinea-Bissau’s current standard of care. This is not, as initially reported in some places, a vaccine-versus-placebo design.

But that doesn’t make it unproblematic.

Randomizing infants to delayed protection from a proven intervention—in a high-prevalence country, to study speculative “non-specific effects” of vaccines—raises real ethical questions. The birth dose exists precisely because early protection matters, especially where perinatal transmission risk is high. Every week of delay is a week of vulnerability. And in a setting with potential loss to follow-up, some infants randomized to the delayed arm may never complete their series at all.

The study reportedly received approval from Guinea-Bissau’s National Ethics Committee. But ethical approval doesn’t automatically mean a study design is beyond critique—particularly when it involves randomizing vulnerable populations to receive less protection than we know how to provide.

Cost-Benefit Analysis Differs Between Countries

The point is made, but there are even more reasons why vaccination schedules differ between countries. When comparing across countries of different sizes and significant differences in healthcare systems, cost analyses vary as well. In countries with universal healthcare, the cost-benefit analysis might be different, especially when transmission of certain diseases is low. Even though vaccines are much cheaper than treating a disease, they still cost something. And when disease incidence is very low, a country might not recommend a universal vaccination or a vaccination at birth. But the U.S. is large and diverse, and its healthcare system has many gaps. So in most cases, vaccines are more cost-effective than the alternative: serious illness and hospitalization. The U.S. even has among the lowest rates of practicing physicians and hospital beds per person, and Americans see physicians less often than people in most other countries. This means it’s much more critical for the U.S. to reduce hospitalizations and severe illnesses than other countries.

The Dose-Counting Problem

Comparing countries gets even more complicated when considering dose counts. Beyond comparing how many diseases are on the vaccine schedule, we often hear claims that American children get “so many more shots” than children in other countries. But this comparison is just as misleading as the disease count. Annual vaccines can really make dose counts explode. For example, flu vaccines are recommended annually for all children 6 months and older. From age 6 months to 18 years, that’s approximately 17-18 doses of flu vaccine. COVID-19 shots add multiple additional doses. So even if the U.S. and Denmark had identical schedules for all other vaccines, annual flu vaccines alone would make U.S. dose counts appear dramatically higher. That’s not “more vaccines”. It’s the same vaccine, repeated, because the virus evolves and updates are needed each year.

Combination vaccines also make dose comparisons nearly meaningless. Multiple vaccines can be bundled into a single shot, and the specific combinations can differ from country to country. The U.K., for instance, uses a 6-in-1 vaccine that protects against hepatitis B, tetanus, diphtheria, pertussis, polio, and Hib. The U.S. has several combination options (such as Pediarix, which covers DTaP, polio, and hepatitis B, and Pentacel, which covers DTaP, polio, and Hib). Two countries could be protecting against the same diseases, but they may appear to give very different numbers of shots simply because the vaccines are packaged differently.

So when someone expresses alarm at the number of doses kids get in the U.S. compared to elsewhere, it’s important to ask how many of those are annual flu shots and how the doses have actually been counted.

Blending routine with non-routine vaccines (such as risk-based recommendations, catch-up schedules, and special-situation doses) can also inflate total numbers that don’t reflect what most children actually receive. Both the U.S. and Denmark have risk-based recommendations beyond their routine schedules, but they can differ, and baseline comparisons can get muddied in public discourse.

Some Countries Have a Higher Illness Tolerance Than Others

Another factor in vaccine schedules is disease tolerance. Denmark has historically had a higher tolerance for disease and, in some cases, has chosen illness over vaccination. For example, the rate of chickenpox (number of cases per population) is much higher than in the U.S. This nuanced decision could be debated and analyzed, but it must take into account that health care costs in the U.S. are at critical levels, and Americans do not have access to free healthcare like in Denmark. So reducing hospitalizations, illness, and health care costs is a much higher priority for the U.S.

Japan: A Comparison That Backfires

Japan is often invoked alongside Denmark as evidence that the U.S. vaccinates more than its peers, but this comparison reveals just how selective the “align with peers” argument really is. Japan’s vaccine system divides vaccines into “routine” (publicly funded) and “voluntary” (often self-paid) categories, making direct comparison misleading. More importantly, Japan routinely vaccinates children against diseases that the U.S. does not: Japanese encephalitis and tuberculosis. So if the logic is to align with peer-country schedules, does that mean we should add vaccines for these two infections to the U.S. schedule? Of course not. Those diseases aren’t endemic in the U.S. Japan can’t be cited as a model for doing less when Japan includes vaccines that the U.S. appropriately doesn’t use. This selective citation seems to promote minimizing vaccines first, then finding international examples as post-hoc justification.

We’ve seen what happens when countries weaken their schedules. Japan withdrew its combined MMR vaccine in 1993 over concerns about a specific mumps strain, then made mumps vaccination voluntary. The result: decades of mumps outbreaks, rubella outbreaks that caused congenital rubella syndrome, and Japan didn’t achieve measles elimination until 2015, years behind countries that maintained strong MMR vaccination programs. That’s not a model. It’s a warning.

The Bottom Line

Americans are not protected through our healthcare system like other high-income countries. We also face unique challenges, such as a large and diverse population. This means that our most vulnerable need special protection through safety nets, like robust vaccine recommendations. If we had Denmark’s healthcare system, perhaps we could have Denmark’s vaccine schedule. We don’t. And until we do, our kids need the protection we actually have.

Stay Curious,

Unbiased Science

P.S. Want more? We also put together a briefing on this topic over at The Evidence Collective.