Characteristics of 5-year-olds who catch up with the combined measles, mumps, and rubella vaccine: findings from a contemporary UK cohort

Abstract Background The national measles, mumps, and rubella (MMR) catch-up programme, launched in April, 2013, aims to increase vaccine uptake in groups with low immunisation rates. Cover of Vaccination Evaluated Rapidly (COVER) provides routine data for monitoring of national and local immunisation coverage; however, records are not held at the individual level and cannot be used to examine vaccine catch up or individual-level characteristics associated with uptake. We examined predictors of catch up with MMR in a contemporary cohort of children targeted by the catch-up programme. Methods We used data from the most recent UK cohort, the Millennium Cohort Study (MCS). Families of children born in the UK in 2000–02 were contacted via opt-out letters; data were collected from 18 818 children, of whom 18 296 were singletons. At ages 3 and 5 years, participants were followed up by letter, telephone (when possible), and a visit. 12 989 (71%) singleton children from the initial cohort responded to all three sweeps. We analysed data for 751 (6%) children who were unimmunised with the MMR at age 3 years. We estimated unadjusted risk ratios (RRs) and 95% CIs for partial (received one MMR) and full (two MMRs) catch up by age 5 years (baseline: remaining unimmunised) according to various social, economic, and demographic characteristics and reasons reported by parents for not immunising their child at age 3 years. Significantly associated variables in univariable analyses (p Findings 440 of 751 children (60·3%, 95% CI 56·2–64·3) remained unvaccinated; 127 (16·1%, 13·3–19·3) partially and 184 (23·6%, 20·1–27·5) fully caught up. In multivariable models, children from families who did not speak English at home were nearly five times more likely to partially catch up than were children living in homes where only English was spoken (RR 4·68, 95% CI 3·63–6·03); full catch up was also more likely in this group (1·90, 1·08–3·32). Children were more likely to fully catch up if they were from Pakistani or Bangladeshi (2·40, 1·38–4·18) or other ethnic origins (1·88, 1·08–3·29) compared with if they were white British; living in socially rented accommodation compared with owner occupiers (1·86, 1·34–2·56); and living outside compared with inside London (1·95, 1·32–2·89). Full catch up was less likely if parents reported medical reasons (RR 0·43, 95% CI 0·25–0·74) or a conscious decision (0·33, 0·23–0·48) for not immunising at age 3 years (compared with practical reasons). Interpretation Parents of children who partially or fully caught up with MMR experienced practical barriers to receiving immunisation (such as missing an appointment) and were from ethnic minority or disadvantaged groups. Time to uptake could be minimised in these families by reducing practical barriers—eg, by providing information in community languages and offering vaccination in alternative settings. Families who continued to reject MMR were from more advantaged backgrounds and made a conscious decision to not immunise early on. Families should be given opportunities to discuss concerns with health professionals, who in turn should be trained for effective communication about immunisation. Our findings refer to a period with high parental concerns around the safety of the vaccine and low incidence of measles. Predictors of catch up in families with young children might differ during times of measles outbreaks. Still, professionals striving to increase MMR uptake should consider these findings in light of the characteristics of their local populations. Funding The Centre for Paediatric Epidemiology and Biostatistics is supported in part by the MRC in its capacity as the MRC Centre of Epidemiology for Child Health. Research at the UCL Institute of Child Health and Great Ormond Street Hospital for Children receives a proportion of the funding from the Department of Health's NIHR Biomedical Research Centres funding scheme. AP is funded by a MRC fellowship.