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Monitoring of timely and delayed vaccinations: a nation-wide registry-based study of Norwegian children aged < 2
Øystein Rolandsen Riise1, Ida Laake2, Marianne Adeleide Riise Bergsaker3
1Division of Infectious Disease Control, Department of Vaccines, Norwegian Institute of Public Health, P.O. Box 4404, Nydalen, NO-0403, Oslo, Norway. oeri@fhi.no.
Insights
Delayed childhood vaccinations are common, affecting nearly half of children and increasing risks for vaccine-preventable diseases. Monitoring these delays is crucial for improving vaccination programs and public health outcomes.
Area of Science:
- Public Health
- Epidemiology
- Immunization Practices
Background:
- Delayed vaccinations heighten the risk of vaccine-preventable diseases (VPDs).
- National immunisation registry monitoring for delayed vaccinations, particularly for two-dose primary series like pertussis, remains understudied.
- Systematic surveillance of all vaccinations can enhance the effectiveness of immunisation programmes.
Purpose of the Study:
- To investigate the frequency and patterns of delayed childhood vaccinations using a national immunisation registry.
- To identify demographic and temporal factors associated with vaccination delays.
- To assess the utility of immunisation registries for monitoring vaccination coverage.
Main Methods:
- Utilized data from the Norwegian immunisation registry (SYSVAK) for children born in 2010 (n=63,382) up to 730 days of age.
- Defined timely vaccinations as those received within 7 days of the recommended age.
- Classified vaccinations as delayed if received over one month past the scheduled date.
Main Results:
- 44.7% of children experienced delays in at least one routine vaccination, with a mean delay of 139 days.
- Significant variations in delay rates were observed across different counties (37.4%-57.8%).
- Immigrant children (52.3%) and those with vaccinations scheduled in July (6.5%) showed higher rates of delay compared to non-immigrant children and other months, respectively.
Conclusions:
- Vaccination delays are frequent in Norway, impacting almost half of the children studied.
- Delays are unevenly distributed, disproportionately affecting immigrant populations and occurring more often during summer vacation periods.
- Continuous monitoring via national immunisation registries is recommended for annual assessment and improvement of vaccination programmes.
Background:
Delayed vaccinations increase the risk for vaccine preventable diseases (VPDs). Monitoring of delayed vaccinations by using a national immunisation registry has not been studied in countries recommending a two-dose (3 and 5 months of age) primary series of e.g., pertussis vaccine. Surveillance/monitoring of all vaccinations may improve vaccination programmes functioning.
Methods:
We obtained information from the Norwegian immunisation registry (SYSVAK) on all programme vaccinations received at age up to 730 days in children born in 2010 (n = 63,382). Timely vaccinations were received up to 7 days after the recommended age. Vaccinations were considered delayed if they were received more than one month after the recommended age in the schedule.
Results:
In vaccinated children, timely administration of the subsequent three doses of pertussis and one dose of measles occurred in 73.8, 47.6, 53.6 and 43.5 % respectively. Delay for one or more programme vaccinations (diphtheria, tetanus, pertussis, polio, Haemophilus influenza type B, invasive pneumococcal disease, measles, mumps or rubella) was present in 28,336 (44.7 %) children. Among those who were delayed the mean duration was 139 days. The proportion of children that had vaccinations delayed differed among counties (range 37.4 %-57.8 %). Immigrant children were more frequently delayed 52.3 % vs. 43.1 %, RR 1.21 (95 % CI 1.19, 1.24). Children scheduled for vaccines in the summer holiday month (July) were more frequently delayed than others (1(st) dose pertussis vaccine 6.5 % vs. 3.9 % RR 1.65 (95 % CI 1.48, 1.85). Priming against pertussis (2(nd) dose), pneumococcal (2(nd) dose) and measles (1(st) dose) was delayed in 16.8, 18.6 and 29.3 % respectively.
Conclusion:
Vaccinations were frequently delayed. Delayed vaccinations differed among counties and occurred more frequently during the summer vacation (July) and in the immigrant population. Monitoring improves programme surveillance and may be used on an annual basis.
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