WASHINGTON, December 26, 2025 – Babies who fall behind on their vaccinations at 2 months are significantly less likely to receive teh measles, mumps, and rubella (MMR) vaccine by age 2, raising concerns about declining immunity rates as the U.S. faces its highest number of measles cases in over three decades.
Early Vaccine Delays Foreshadow Later Gaps
A new study reveals a strong link between initial vaccination timing and long-term immunization adherence, particularly crucial amid a resurgence of preventable diseases.
- Babies who don’t get their initial vaccines on schedule at 2 months are over seven times more likely to miss their MMR shot by age 2.
- The U.S. registered 2,065 confirmed measles cases as of December 30, 2025, the highest annual total in more than 30 years.
- Pediatricians may have a limited window to build trust and educate parents about the importance of timely vaccinations.
- Declines in vaccination rates are linked to distrust of public health authorities and reactions to pandemic-era measures.
The study, published Friday in JAMA Network Open, analyzed health records from approximately 322,000 children born between 2017 and 2023. Researchers found that those who didn’t receive their initial vaccinations on time-as recommended by the Centers for disease Control and Prevention-were far more likely to experience further delays or complete omission of the MMR vaccine, typically administered between 12 and 15 months, with a second dose between ages 4 and 6.
“There’s evidence from this study that very early vaccination delays lead to later vaccination delays and even missed vaccination for measles,” said Nina Masters, an epidemiologist and lead author of the paper. “This shows that hesitancy is really starting early and has a long arc.”
A significant indicator of timely MMR vaccination was whether babies received the vaccines recommended at 2 months-including hepatitis B, rotavirus, diphtheria, tetanus, pertussis, polio, Haemophilus influenzae type b, and pneumococcal disease. Pediatricians frequently enough use combination vaccines to administer multiple protections with fewer injections.
Masters suggests pediatricians should initiate conversations with parents about vaccination-and the importance of staying on schedule-before the 2-month appointment. “The three biggest influences on vaccination are past vaccine receipt, intending to vaccinate, and a doctor’s advice,” Brewer added. “The most promising avenue for intervention is a doctor’s recommendation.”
The American Academy of Pediatrics recommends frequent check-ups in the first year of life, including visits within the first week, at 1 month, 2 months, 4 months, 6 months, and 9 months. However, the study found that just under half of the babies studied followed this schedule. This number was likely lower among children without consistent access to healthcare or insurance.
“I think it’s conservative,” Masters said, suggesting the findings may underestimate the problem. “I think if we had a way to look at the parents that aren’t bringing their children in, that aren’t vaccinating their children, that don’t have a medical home-which we don’t have the ability to do-we would likely see lower coverage, lower timeliness.”
Masters also noted that recent changes to vaccination policy, including a December decision by the CDC’s advisory committee to alter the hepatitis B vaccination schedule, could have further implications. The CDC now recommends at-birth vaccination only for babies whose mothers tested positive for hepatitis B or whose status is unknown.
Researchers are continuing to investigate the potential impact of these policy shifts on overall vaccination rates.
