Jan 03, 2026
3 min read
Children who miss early vaccinations are much more likely to not receive the measles, mumps and rubella (MMR) vaccine by age two, according to a new study released Friday.
Children not vaccinated early are more likely to miss MMR by age 2: study
This comes as the US surpasses 2,000 measles cases for the first time in 33 years.
Children who do not receive early vaccines are more likely not to receive the measles, mumps and rubella (MMR) vaccine by age 2, a new study shows.
The United States recently surpassed 2,000 cases of measles for the first time in more than 30 years, according to the Centers for Disease Control and Prevention (CDC).
MMR vaccinations have declined over the past few years, according to CDC data, but the authorities say they have learned well that vaccinations have been delayed or dropped in connection with the COVID-19 pandemic.
For the new study, published Friday in the journal JAMA Network Open, the team examined data from Truevat, a collection of electronic health records that includes several US health systems.
Participants included more than 321,000 children who received regular care during the first two months, first year and second year of life between January 1, 2018 and April 30, 2025.
The CDC currently recommends that people receive two doses of the MMR vaccine, the first at age 12 to 15 months and the second at age 4 to 6 years.The CDC says one dose is 93% effective and two doses are 97% effective against measles.
Most children in the study received the MMR vaccine on time, with 78.4% doing so.
The study found that approximately 13.9% of children delayed vaccination, 1% received the MMR vaccine earlier, and 6.7% did not receive the MMR vaccine before the age of 2 years.
The study found that the strongest predictor of non-adherence to the MMR vaccine was delay in receiving the recommended vaccinations by 2 to 4 months.
These early vaccines included diphtheria, tetanus, and pertussis (DTAP);Haemophilus influenzae type B (HIB);Pneumococcal Conjugate Vaccine (PCV);and inactivated poliovirus (IPV) vaccines.
Nina Masters, who led the study and is a senior research scientist at Truveta, told ABC News that it's not uncommon for children who miss vaccines early to miss them later, but it points to some parents' reluctance to vaccinate their children at a young age.
"It also means that the opportunity for them to intervene and involve parents by providing more education about the safety and effectiveness of vaccines should happen in advance," they say."This can be difficult as parents may have time to form a strong relationship with their child's pediatrician, but this study highlights the importance of pediatric providers to discuss vaccinations and build trust quickly with parents."
The results of the study showed that those who received their 2-month vaccination on time were seven times more likely to receive the MMR vaccine.
The team found that the percentage of children who received the MMR vaccine on time changed during the school year, rising from 75.6% in 2018 to 79.9% in 2021 and then declining to 76.9% by 2024.
According to the study,Between 2021 and 2024, this decline is associated with an increase in the proportion of children who have not received the MMR vaccine at age 2 years.It will increase from 5.3% in 2020 to 7.7% in 2024.
The study found that children most likely to receive the MMR vaccine before age 2 were boys, white, non-Hispanic or Latino.
According to the study, living in a rural area increases the risk of not receiving the MMR vaccine, even among children receiving usual care.
The study included only children with regular access to child care, so the actual vaccine delay in the broader US population may be worse.
The authors added that these results suggest increasing vaccine hesitancy or unmeasured access challenges, highlighting the importance of timely intervention so that children are less likely to delay or skip vaccination.
Dr. Amesh Adalja, a senior scholar at the Johns Hopkins Center for Health Security who was not involved in the study, said the findings have significant public health implications because there are questions about whether the US will maintain the status of smallpox elimination and increasing vaccination is "the way out of this problem."
"If we want to live in a society where measles is a problem of the past, where we don't have to think about it, where schools don't have to make emergency plans and where our children don't die needlessly from measles, that's why we need to get vaccinated," he told ABC News.
Adilja added that vaccination not only protects a person against infection, but also benefits the community.
"The higher the vaccination rates in a community, the more resilient the community will be to these infectious diseases," he said.
Crystal Richards, MD, MS, is a pediatric resident at New York Presbyterian Hospital Columbia University Medical Center and a member of the ABC News Medical Department.
