RECENT data show that timely measles, mumps, and rubella (MMR) vaccination in young children has decreased in the years following the COVID-19 pandemic. In a cohort study of 321,743 infants across the USA, researchers found that timely MMR receipt by 2 years of age fell by three percentage points between 2021 and 2024. This decline is particularly concerning as measles cases in the USA reached 1,723 by November 2025, the highest level since elimination in 2000.
Early Vaccination Delays Predict Later Missed MMR Doses
The study highlights a clear pattern: infants who were late receiving their standard 2- and 4-month vaccinations were significantly more likely to miss MMR entirely by 2 years of age. Specifically, children late on 2-month vaccines were nearly seven times more likely not to receive MMR (adjusted odds ratio [AOR] 6.96), while late 4-month vaccines increased the risk over sixfold (AOR 6.16). These findings underscore the critical importance of early adherence to routine vaccination schedules.
Impact of Regular Healthcare Access
Importantly, this study included children with regular access to primary care, suggesting that missed or delayed MMR vaccinations are not solely due to healthcare inequities. Instead, delays in early infant vaccines may serve as a red flag for clinicians, signalling children at higher risk of falling behind on subsequent immunisations. Monitoring adherence to early vaccine schedules could allow for timely interventions, including reminders, catch-up appointments, or additional parental counselling.
Post-Pandemic Trends and Implications
MMR coverage showed improvement up to 2021, with timely vaccination rates reaching nearly 80%, but the post-pandemic decline highlights a setback in public health efforts. The COVID-19 pandemic disrupted routine healthcare visits and may have contributed to delays in early infant immunisations. These disruptions could increase susceptibility to outbreaks of measles and other preventable diseases if unaddressed.
Opportunities for Clinicians and Healthcare Systems
Healthcare providers play a vital role in maintaining vaccination coverage. Identifying children who are late on 2- and 4-month vaccines offers a practical opportunity to prevent later gaps in MMR coverage. Proactive scheduling, parental education, and follow-up reminders can mitigate the risk of missed vaccines. In doing so, clinicians not only protect individual children but also strengthen herd immunity and reduce the likelihood of vaccine-preventable disease outbreaks.
Reference
Masters NB et al. Delayed or absent first dose of measles, mumps, and rubella vaccination. JAMA Netw Open. 2026;9(1):e2551814.
