Title: Late or missed childhood vaccination: identifying the determinants and estimating the impact on subsequent child health outcomes.
Funder: Department of Health and Social Care

Abstract: BackgroundLate 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? AimsImprove 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. Objectivesi)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. MethodsThree, 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. ImpactFindings will inform how children's vaccine services can improve to increase vaccine uptake and protect more children against infectious diseases.

Lay abstract: Vaccines protect children against serious infectious diseases and prevent disease outbreaks. Most children in the United Kingdom are vaccinated on time, but some are vaccinated late or miss getting vaccinated. It is important that all children get all their recommended vaccines, at the recommended ages. Unvaccinated children are at risk of getting ill from infectious diseases. If lots of children in the population are not vaccinated, then outbreaks of infectious diseases become more common. For example, not enough children in England have been getting two doses of the Measles, Mumps and Rubella(MMR) vaccine recently, causing more measles outbreaks.My research aims to understand which children in England are unvaccinated. I will see if children whose mothers are vaccinated in pregnancy are more likely to get vaccinated. I will also study how vaccines can benefit long-term health and explore why parents think some children miss being vaccinated or get vaccinated late. My findings could help improve vaccine services and increase how many children are vaccinated. My research will involve three studies using general practice(GP) records and one study involving working with a mother's community group in North-West London. Studies 1-3 will use a database of anonymous GP records called the Clinical Practice Research Datalink(CPRD) to investigate childhood vaccination. Babies born between 2000-2017 will be identified and then their GP visits followed up, until 2018. A large childhood vaccine study like this, using CPRD records, has not been done before. In study 1, I will describe which children are vaccinated late or miss getting vaccinated. For example, how vaccination is different between children living in areas that are less affluent and between children from different ethnic groups. In study 2, I will link mother's and children's GP records to see if mothers of unvaccinated children are different from mothers of vaccinated children. I will see if mothers of unvaccinated children are less likely to receive their pregnancy vaccines. In study 3, I will measure if being vaccinated on time means children visit their GP less and are prescribed less antibiotics. This is important as vaccines may reduce the risk of children becoming ill from other illnesses as well as preventing specific infectious diseases. In study 4, I will partner with a mother's group called the Mosaic Community Trust (Mosaic) which is based in an area of North-West London called Church Street. In Church Street not enough children get vaccinated. For example, only 78% of children got their first MMR vaccine by the age of 2 years compared to 90% of children in England. Mosaic, is a group of around 150 local black and ethnic minority mothers, including some who have been trained as community health workers. We have worked together before on a public involvement project about pregnancy vaccines. This time we have agreed to co-create a research questionnaire to ask local parents why they think children aren't getting vaccinated locally. The questionnaire will ask how they feel about childhood vaccines and how easy it is for them to get their children vaccinated locally. Church Street has had low childhood vaccine rates for many years, but local people have not been asked why they think this is, so, Lena Choudary-Salter, the head of Mosaic, named the project: 'Why has nobody asked us?!'. My findings will be shared with parents, doctors, midwives and health visitors locally in North-West London and across the UK. I hope my findings will help improve vaccine services and provide more information for parents and doctors about how vaccines benefit long-term child health. I aim to increase the number of children getting vaccinated and protected against dangerous infectious diseases.

Research activity codes: 3.4 VACCINES
Health categories: INFECTION