Assessment of on-time vaccination coverage in population subgroups: A record linkage cohort study
Hannah C Moore1, Parveen Fathima1, Heather F Gidding2
1Wesfarmers Centre of Vaccines and Infectious Diseases, Telethon Kids Institute, The University of Western Australia, PO Box 855, West Perth, WA 6872, Australia.
Insights
On-time infant vaccination coverage in Australia varies significantly by population group, with Aboriginal infants and those from disadvantaged backgrounds showing lower rates. Targeted programs are needed to improve timely diphtheria-tetanus-pertussis (DTP) vaccine administration for these vulnerable infants.
Area of Science:
- Public Health
- Epidemiology
- Immunization Practices
Background:
- Infant vaccination coverage in Australia exceeds 90% by 12 months.
- Timeliness of infant vaccination, particularly the 2-4-6 month schedule, and coverage in specific populations are underreported.
- Diphtheria-tetanus-pertussis (DTP) vaccines are crucial for early childhood protection.
Purpose of the Study:
- To assess on-time diphtheria-tetanus-pertussis (DTP) vaccination coverage across various demographic and perinatal factors in a large Australian birth cohort.
- To identify specific population subgroups with suboptimal on-time DTP vaccination.
- To highlight potential public health risks associated with delayed infant immunizations.
Main Methods:
- A population-based cohort study linked individual birth, perinatal, and immunization records for 1.9 million Australian births (1996-2012).
- On-time DTP vaccination was defined as administration within 14 days prior to 30 days after the scheduled due date.
- Coverage was analyzed across 13 demographic and perinatal characteristics, including Aboriginal status, maternal parity, smoking, and socioeconomic status.
Main Results:
- On-time DTP coverage for non-Aboriginal infants was 88.1% (2mo), 82.0% (4mo), and 76.7% (6mo), with 91.3% 3-dose coverage by 12 months.
- On-time DTP coverage for Aboriginal infants was lower: 77.0% (2mo), 66.5% (4mo), and 61.0% (6mo), with 79.3% 3-dose coverage by 12 months.
- Significant disparities were observed: infants of mothers with ≥3 pregnancies had lower on-time coverage (62.5% vs. first-borns), smoking mothers' infants had 8.7-10.3 percentage points lower coverage, and increasing socioeconomic disadvantage correlated with decreasing on-time coverage.
Conclusions:
- On-time coverage of the 2-4-6 month DTP schedule falls to 50-60% in certain subgroups, posing an avoidable public health risk.
- Aboriginal infants, infants of multiparous mothers, and those from socioeconomically disadvantaged backgrounds are key groups requiring targeted interventions.
- Improving vaccination timeliness in these vulnerable populations is essential for maximizing public health benefits and reducing vaccine-preventable disease risks.
Abstract:
Reported infant vaccination coverage at age 12 months in Australia is >90%. On-time coverage of the 2-4-6 month schedule and coverage in specific populations is rarely reported. We conducted a population-based cohort study of 1.9 million Australian births, 1996-2012, combining individual birth and perinatal records with immunisation records through probabilistic linkage. We assessed on-time coverage across 13 demographic and perinatal characteristics of diphtheria-tetanus-pertussis vaccines (DTP) defined as vaccination 14 days prior to the scheduled due date, to 30 days afterwards. On-time DTP vaccination coverage in non-Aboriginal infants was 88.1% for the 2-month dose, 82.0% for 4-month dose, and 76.7% for 6-month dose; 3-dose coverage was 91.3% when assessed at 12 months. On-time DTP coverage for Aboriginal infants was 77.0%, 66.5%, and 61.0% for the 2-4-6 month dose; 3-dose coverage at 12 months was 79.3%. Appreciable differences in on-time coverage were observed across population subgroups. On-time coverage in non-Aboriginal infants born to mothers with ≥3 previous pregnancies was 62.5% for the 6-month dose (47.9% for Aboriginal infants); up to 23.5 percentage points lower than for first-borns. Infants born to mothers who smoked during pregnancy had coverage 8.7-10.3 percentage points lower than infants born to non-smoking mothers for the 4- and 6-month dose. A linear relationship was apparent between increasing socio-economic disadvantage and decreasing on-time coverage. On-time coverage of the 2-4-6 month schedule is only 50-60% across specific population subgroups representing a significant avoidable public health risk. Aboriginal infants, multiparous mothers, and those who are socio-economically disadvantaged are key groups most likely to benefit from targeted programs addressing vaccine timeliness.
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