A major new study has revealed that millions of children in low- and middle-income countries are receiving routine vaccinations weeks or even months later than recommended, potentially leaving them vulnerable to serious diseases during critical stages of early life.
Researchers analyzed vaccination data from more than 460,000 children under the age of three across 91 countries and found that delays remain common despite improvements in overall vaccination coverage. While many children eventually receive their vaccines, the study highlights that late immunization can reduce the effectiveness of public health programs by extending the period when children are unprotected.
The research found that only about half of measles vaccine doses and third doses of diphtheria, tetanus, and pertussis (DTP3) vaccines were administered within the recommended time frame. Average delays ranged from approximately three weeks for some vaccines to nearly eight weeks for DTP3, one of the most delayed routine childhood immunizations.
Health experts warn that vaccine timing is critical because immunization schedules are carefully designed to protect children when they are most vulnerable to infection. Delays in vaccines for diseases such as hepatitis B, pertussis, and measles can increase the risk of severe illness and contribute to higher mortality rates at the population level.
The study also raised concerns about the hepatitis B birth dose, which should ideally be administered within 24 hours of birth to prevent mother-to-child transmission. Researchers found that only half of these doses were given within the recommended period.
Experts say national vaccination coverage figures alone may not provide a complete picture of immunization program performance. They are calling for greater focus on vaccine timeliness as an additional measure to identify gaps in healthcare delivery and improve protection for vulnerable children worldwide.
The findings suggest that monitoring both vaccination coverage and timing could help countries strengthen immunization programs, reduce preventable diseases, and ensure children receive protection when they need it most.
