Under the leadership of Secretary of Health and Human Services Robert F. Kennedy Jr., an anti-vaccine activist, the current childhood vaccination schedule in the United States has come under scrutiny. In early December, the Centers for Disease Control and Prevention's vaccine advisory panel voted to change its recommendation that all newborns receive the hepatitis B vaccine. The panel, without presenting new evidence, suggested that children wait until they are two months old to be protected against the incurable, contagious liver disease. Another changes in vaccination recommendations may be planned for 2026.
The current schedule of childhood vaccinations in the United States, Developed by infectious disease experts, epidemiologists, pediatricians and other scientists, it is based on the maturation of children's immune systems and when they are most susceptible to viruses and other germs.
Babies protected from nine diseases
In the first few months of a child's life, vaccinations are currently recommended to protect against nine infectious diseases. In addition to RSV and the first hepatitis B shot (second shot at 1 to 2 months of age and third shot at 6 to 18 months), first doses of five vaccines are given: diphtheria, tetanus, and pertussis (DTP); rotavirus, which protects against life-threatening diarrheal disease; polio; pneumococcal; And Haemophilus influenzae infection type b (Hib), an infection that can lead to meningitis.
Typically, the first dose of MMR vaccine is given between 12 and 15 months of age, and the second dose between 4 and 6 years of age. To provide the best protection, several vaccines, including MMR, must be divided into several doses, the timing of which is determined after decades of research.
Among children included in the study, the rate of timely first dose of MMR vaccine decreased from 79.9% in 2021 to 76.9% in 2024. The study found that boys and children living in rural areas were slightly less likely to receive the MMR vaccine than the average child.
Because the study only included children with regular access to health care, it is likely that the numbers are even lower in the general population.
“These numbers are conservative in terms of the size of these effects if we included the general population,” Masters said.
Angela Rasmussen, a virologist at the University of Saskatchewan, Canada, said the main problem with the vaccine delay is that “while that delay is in effect, you will be unprotected for a longer period of time.”
She said concerns about the timing of vaccinations, that children are getting too many shots at once or that combination vaccines are dangerous are unfounded. “There is no evidence that any of this exists.”
Risks of delaying first doses
“Our current vaccination schedule has been decided over many years and to gather quite a lot of data to show that this is actually the time to vaccinate people when the risks are minimized and the benefits are maximized,” Rasmussen said.
New research suggests that changes in children's schedules, such as delaying hepatitis B vaccinations, could sow mistrust and have “compounding effects” on other vaccines, Masters said. “Children will be less likely to get vaccinated against all types of diseases, which means more children will be at risk, which is a frightening reality.”
This is especially true for MMR doses.
Dr. Nathan Law, an assistant professor of infectious diseases at Stanford University, said, “If the first dose is delayed even further, say by two years or whatever, then there will be an even larger window for differences in susceptibility to develop that put children at risk for measles, especially as measles begins to spread more in the United States.”
More than 2,000 cases of measles were reported in the United States in 2025, the highest number since 1992.
“Measles is kind of the canary in the coal mine, the smoke alarm,” said Dr. Lee Harrison, a professor of epidemiology and medicine at the University of Pittsburgh.
“When you start to see declines in enrollment rates, you start to see outbreaks,” Harrison said. “And that's what we see.”
Problems of pediatricians
New research shows the importance of the relationship between pediatricians and parents.
An NBC News/Stanford University data study found that among states that collect data on the MMR vaccine, 67% of counties and jurisdictions now have child care immunization rates below 95%—the level of herd immunity doctors say is needed to protect against an outbreak.
“If you look at who gets measles, it's certainly people who are not vaccinated, but a lot of cases occur in children, and a lot of cases occur in children before they get their first dose, so often within that 6 to 12 month period,” said Law, lead co-author of the NBC News data investigation.
The immunity a baby receives from its mother wears off at about 6 months, but the first dose of MMR vaccine is not given until after 12 months.
However, vaccine hesitancy may not be the only reason for this decline.
“People have barriers to care: it’s hard to get to a clinic, it’s hard to get an appointment, it’s hard to find free time to pick up their child. Or it could be a strong belief in wanting to follow some alternative delayed vaccination schedule,” Lo said. “The practical implication is that the minute a doctor sees that a child is not up to date on their vaccines, it certainly draws your attention to what can be done.”
The report shows the challenges pediatricians face in building trusting relationships with new parents, Masters said.
“What that means is that pediatricians need to get really involved early and immediately on vaccine issues, provide education, provide a safe place for parents to ask questions, and provide reassurance that vaccines are safe and effective, really before that two-month visit,” she said.
