Title: Are children who receive their first Measles Mumps and Rubella (MMR1) vaccination by 24 months more likely to share a household with older non-vaccinated children?

Problem

No UK country reaches the WHO target of 95% MMR1 coverage by age 24 months, essential for herd immunity (1), and this has worsened during the pandemic, increasing the risk of a measles outbreak (2). National data do not examine coverage across all children sharing the same household. We used primary care electronic health records to link people in households (3) and explored associations between household characteristics and MMR coverage. Specifically, we examined whether children receiving their MMR1 by 24 months were more likely to share a household with children also not vaccinated by this age and variation in coverage by ethnic background and household composition.

Approach

We identified all children born between 2014-2019, eligible for MMR1 and sharing a household with at least another child from the primary care EHRs of 1,192,630 children registered with general practitioners in North East London between 2001-2021. We identified household members at the MMR1 date of our cohort of interest (3). We estimated the proportion (95% Confidence Interval [CI]) of children receiving MMR1 by age 24 months. We calculated mutually adjusted prevalence ratios (PR) by sex, ethnicity, deprivation (Index of Multiple Deprivation (IMD) quintiles), household size and household composition to examine household-level associations in MMR1 coverage

Findings

We identified 70,968 children (36186 [50.9%] boys) from 8,3517, households, of whom 18,417 (26.0%), 19,961 (28.1%), 5817 (8.2%), 6680 (9.4%) were from White, South Asian, Black, and Mixed/Other ethnic backgrounds respectively (20,093 (28.3%) ethnic codes missing). Overall, 67,527 (80.9%) children in eligible households received an MMR1 by 24 months, of whom 95.7% were living with children who also received it by this age. After mutual adjustment for sex, ethnicity, deprivation and household composition, children from South Asian ethnic backgrounds (PR 1.01; 95% CI: 1.00,1.01 ) were more likely, and those from mixed ethnic backgrounds (PR: 0.98; 95% CI: 0.97,0.99), living in single adult households (PR: 0.97, 95% CI: 0.97-0.98) or in households with >4 children (PR: 0.96, 95% CI: 0.95-0.96) less likely, to receive MMR1 by 24 months of age.

Consequences

Household composition is associated with MMR1 coverage. Children living in single adult households or with larger numbers of children are less likely to receive MMR1 by 24 months. Further work is needed to explore the reasons for this and identify actionable opportunities using data-enabled primary care interventions to reduce vaccination inequalities and prevent measles outbreaks. 1)http://bit.ly/3DZjUCG2)http://dx.doi.org/10.1136/bmjopen-2022-0662883) DOI: 10.23889/ijpds.v6i1.1674