Late or missed childhood vaccination: identifying the determinants and estimating the impact on subsequent child health outcomes.

Background Late or missed vaccination puts individual children at risk of infectious diseases and increases the likelihood of outbreaks.

England's overall high vaccination rates are declining and recent variable measles, mumps and rubella(MMR) vaccine uptake has contributed to increased measles outbreaks.

Vaccine uptake is related to health system barriers and parental attitudes, with lower uptake among some ethnicities and poorer children.

Pregnant women are offered pertussis vaccine, but the relationship between mother's and children's vaccine uptake is unknown. There is evidence that vaccines benefit overall child health beyond preventing specific infections.

Vaccination could reduce antibiotic prescribing either directly through preventing bacterial illnesses or indirectly by preventing unnecessary antibiotic prescriptions for viral infections. However, the impact of missed or late vaccination on subsequent primary-care use and antibiotic prescribing is unknown.

Research Questions 1.Which children are at risk of being vaccinated late or missing vaccines before 5-years old? 2.Do children whose mothers are not vaccinated in pregnancy have a higher risk of being vaccinated late or missing vaccines before 5-years old? 3.Do children who are vaccinated late or who miss vaccines before 5-years old have higher annual rates of primary-care consultations and antibiotic prescribing? 4.Why do parents think children are being vaccinated late or missing vaccines?

Aims Improve childhood vaccination rates by: i)identifying the key determinants of missed or late childhood vaccination in children's and mother's general practice(GP) records, ii)evaluating vaccines' long-term health benefits and iii)exploring why parents think some children are unvaccinated.

Objectives i)Estimate the proportion of children under 5-years old in a birth cohort with missed or late vaccination and describe their socio-demographic and health-status characteristics. ii)Estimate the risk of missed or late vaccination under 5-years old in children whose mothers do not receive pertussis vaccine in pregnancy. iii)Estimate the impact of missed or late vaccination under 5-years old on children's primary care use and antibiotic prescribing. iv)Explore parents' beliefs about what drives missed or late childhood vaccination.

Methods Three, retrospective birth cohort-studies are proposed using the Clinical Practice Research Datalink(CPRD) GP records database. Study 1 will describe children's vaccination patterns:before 1-year, at 1-year and before 5-years.

Vaccination patterns will be described by sex, ethnicity, deprivation, prematurity, breastfeeding, congenital co-morbidities and chronic illnesses.

Study 2 will link mother's and children's records to estimate the association between maternal pertussis vaccination and childhood vaccinations using a multi-nominal logistic regression model.

Study 3 will estimate the impact of late or missed vaccination on primary care consultation and antibiotic prescribing rates using a Poisson regression model, stratified by age-group.

Study 4, is a qualitative project, using a community based participatory research approach in partnership with the Mosaic Community Trust(Mosaic), a mothers group in North-West London, where vaccine uptake is low. A co-designed questionnaire will explore local parents' views on low childhood vaccine uptake.

Mosaic were previous partners on a pregnancy vaccine public involvement project.

Impact Findings will inform how children's vaccine services can improve to increase vaccine uptake and protect more children against infectious diseases.