Aims The preschool booster vaccine (PSB) is recommended for children between the ages of 3 years 4 months – 5 years. Although the uptake of the PSB is sub-optimal, few studies have explored the reasons for this. This study aimed to establish the uptake, and identify the determinants of PSB uptake. In addition, to examine the association between uptake of primary and MMR vaccinations and the PSB, and explore the reasons given by parents for PSB non-uptake.
Methods The study was based on the UK MCS, a longitudinal study of children born in the UK from 2000-2002. In the third sweep, conducted when the children were 5 years, a detailed immunisation history was collected from parents of 12400 singleton or first-born children. Socio-economic, demographic and health factors considered to be associated with childhood immunisation uptake were evaluated. Sampling and non-response weights were used to adjust for effects of the initial sampling design and attrition between sweeps. Risk ratios (RRs) and 95% confidence intervals (CIs) were estimated using Poisson regression analysis.
Results Only 325 children (2.6%) were reported not to have had the PSB. On adjusted analysis, 3 variables were associated with lower PSB uptake: children born in England (as opposed to other home countries), residing with a lone parent, and having a long-term condition. In addition, a prior history of either partial or non-uptake of primary immunisations, or non-uptake of MMR vaccine was significantly associated PSB non-uptake. The main parental reasons for vaccine non-uptake were that the vaccine was due in the near future; the child was not offered the booster or that the parent did not know the vaccine was due.
Conclusion This is the largest cohort study to date investigating factors determining uptake of PSB. We found high uptake among the MCS children. However, non-compliance with childhood immunisations from an early age correlated with PSB uptake, and the main parental reason for non-uptake at time of the MCS survey was due to deferral rather than refusal of the PSB. Early identification of these families with targeted counselling and reminders may help to improve overall vaccination rates further.