Adherence to hepatitis A and hepatitis B multi-dose vaccination schedules among adults in the United Kingdom: a retrospective cohort study

BACKGROUND: Timely and complete vaccination with multi-dose schedules is of public health importance, because an incomplete vaccination series may yield suboptimal disease protection. However, data on adherence of adults to multi-dose vaccines are limited. We sought to estimate adherence to multi-dose hepatitis vaccination schedules among adults in the United Kingdom (UK). METHODS: This retrospective cohort study was conducted using anonymized electronic health record (EHR) data from the Clinical Practice Research Datalink (CPRD). Individuals aged 19 years and older at their first identified dose of hepatitis vaccine (2009–2016) were included if they had continuous EHR data for 12 months before the first identified hepatitis A dose or for 6 months before the first identified hepatitis B or combination hepatitis A/B dose. We estimated dose and series completion for each vaccine and adherence to recommended vaccination schedules, as well as adherence within additional prespecified time periods after the first vaccine dose, with sensitivity analyses restricted to adults who had available data for up to 24 months after the first dose. Median time to series completion was estimated using Kaplan-Meier methods. RESULTS: Mean (SD) age at initiation was 42 (16) years for hepatitis A (n = 374,881), 40 (16) years for hepatitis B (n = 71,634), and 38 (15) years for hepatitis A/B (n = 10,335). Women comprised 52 to 55% of each vaccine cohort. Overall, 42,294 adults (11%) completed the two-dose hepatitis A vaccine series within the recommended 12 months; and 15,564 (22%) and 1076 (10%) completed the three-dose hepatitis B and hepatitis A/B series, respectively, within the recommended 6 months. These percentages rose to only 23, 35, and 33%, respectively, when the follow-up periods were extended to 36 months for hepatitis A and to 30 months for hepatitis B and A/B vaccines. Median times to series completion within recommended schedules were not reached in any cohort. Sensitivity analyses supported the primary findings for the full cohorts. CONCLUSIONS: Adherence and series completion rates for hepatitis A and B vaccines in the UK are low. Identifying, understanding, and addressing barriers to series completion for multi-dose vaccines for adults in real-world settings are needed. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s12889-019-6693-5) contains supplementary material, which is available to authorized users.