Abstract
BackgroundTimeliness in the administration of recommended vaccines is often evaluated using vaccine delays and provides more information regarding the susceptibility of children to vaccine-preventable diseases compared with vaccine coverage at a given age. The importance of on-time administration of vaccines scheduled at the first visit is well documented, but data are scarce about the impact of vaccine delays at other visits on vaccination status by 24 months of age. Using vaccine delays for the first three doses of DTaP-containing vaccines and for the first dose of measles-containing vaccines as markers of timeliness at the 2, 4, 6 and 12 month visits, we estimated the proportion of incomplete vaccination status by 24 months of age attributable to a vaccine delay at each of these visits.MethodsWe used the data from six cross-sectional coverage surveys conducted in the Province of Quebec from 2006 to 2016 which included 7183 children randomly selected from the universal health insurance database. A vaccine dose was considered delayed if received 30 days or more after the recommended age. The impact of new vaccine delays at each visit on incomplete vaccination status by 24 months of age was estimated with the attributable risk in the population.ResultsThe proportion of children with vaccine delay was 5.4% at 2 months, 13.3% at 4 months, 23.1% at 6 months and 23.6% at 12 months. Overall, 72.5% of all 2-year-old children with an incomplete status by 24 months were attributable with a vaccine delay, of which 16.1% were attributable with a first vaccine delay at 2 months, 10.6% at 4 months, 14.0% at 6 months and 31.8% at 12 months.ConclusionsWhile great emphasis has been put on vaccine delays at the first vaccination visit, the prevalence of vaccine delays was greater with later visits and most children with an incomplete vaccination status by 24 months had a vaccine delay occurring during these later visits. Interventions to improve timeliness should address vaccine delays at each visit and not only focus on the first visit.
Highlights
Timeliness in the administration of recommended vaccines is often evaluated using vaccine delays and provides more information regarding the susceptibility of children to vaccine-preventable diseases compared with vaccine coverage at a given age
While the literature on vaccine coverage put an emphasis on vaccine delays at 2 months, this study shows that the proportion of vaccine delays was greater at later visits increasing from 5.4% at 2 months, to 13.3% at 4 months, to 23.1% at 6 months and to 23.6% at 12 months
Vaccine delay at one visit had an impact on the timing and administration of subsequent doses as most children with vaccine delay for a DTaP-containing vaccine (DTaP) dose received their subsequent dose with a 2-month interval rather than the shortened interval recommended in the accelerated schedule
Summary
Timeliness in the administration of recommended vaccines is often evaluated using vaccine delays and provides more information regarding the susceptibility of children to vaccine-preventable diseases compared with vaccine coverage at a given age. The importance of on-time administration of vaccines scheduled at the first visit is well documented, but data are scarce about the impact of vaccine delays at other visits on vaccination status by 24 months of age. Vaccine coverage is a common indicator used for the evaluation and monitoring of vaccination programs. It evaluates the proportion of individuals who have received all the recommended vaccines, regardless of the timeliness [1]. A vaccine delay for a dose may impact on-time administration of subsequent doses and increase the child’s risk of disease targeted by the vaccine [11, 12]
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