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Immunization status and birth order
1Department of Pediatrics, University of Rochester (NY) School of Medicine and Dentistry, USA.
Insights
Secondborn children are often immunized later than firstborns, particularly if an older sibling also experienced delayed immunizations. This study highlights birth order as a factor in timely childhood vaccinations.
Area of Science:
- Pediatric Health
- Immunization Practices
- Public Health
Background:
- Birth order can influence family dynamics and resource allocation.
- Understanding factors affecting childhood immunization is crucial for public health.
Purpose of the Study:
- To investigate the association between birth order and immunization status in children.
- To determine if secondborn children receive immunizations later than firstborn children.
Main Methods:
- Retrospective medical record review of immunization dates for 892 children (446 matched sibling pairs).
- Analysis focused on diphtheria and tetanus toxoids and pertussis vaccine (DTP) and measles-mumps-rubella (MMR) vaccine administration.
- Compared median ages at immunization and point prevalence of being up-to-date for firstborn vs. secondborn children up to 2 years of age.
Main Results:
- Secondborn children showed significantly lower rates of full immunization between 5 and 12 months compared to firstborns.
- Firstborn children were more likely to receive timely DTP2 and DTP3 vaccinations.
- Secondborn children received DTP2 and DTP3 vaccinations approximately 10 and 20 days later, respectively, than their firstborn siblings.
Conclusions:
- Secondborn children are at higher risk for delayed immunizations compared to firstborn children.
- Delayed immunization in a firstborn child increases the risk of delayed immunization in a secondborn sibling.
Objective:
To determine whether an association exists between immunization status and birth order.
Design:
Medical record review of immunization dates for matched siblings.
Setting:
Pediatric clinic at a university medical center.
Subjects:
A total of 892 children (446 sibling pairs of firstborn and secondborn children) born between 1983 and 1991 who received regular pediatric care at the clinic.
Outcome Measures:
Median ages at which firstborn children and their secondborn siblings had been immunized with the initial four doses of diphtheria and tetanus toxoids and pertussis vaccine (DTP1, DTP2, DTP3, and DPT4) and the initial dose of measles-mumps-rubella vaccine; point prevalences of firstborn and secondborn children up-to-date with all immunizations at each month of life to 2 years of age.
Results:
Between 5 and 12 months of life, the percentage of secondborn children who were fully immunized was significantly lower than the percentage of fully immunized firstborn children (P values ranging from < .0001 to < .05). Firstborn children were much more likely than their secondborn siblings to have been immunized on time with DTP2 (z = 3.80, P = .0001) and DTP3 (z = 3.31, P = .0009). Overall, DTP2 immunizations were given at median ages 10 days later, and DTP3 immunizations, 20 days later to secondborn children than to their firstborn siblings. In addition, late immunization of a firstborn child was found to increase the risk that a secondborn sibling would also be immunized late.
Conclusions:
Secondborn children are likely to be immunized later than firstborn children. Secondborn children with an older sibling who was immunized late are at particular risk for delayed immunizations.