Vaccination coverage: DTaP and IPV booster (5 years) - WMCA

Children for whom the local authority is responsible who completed a booster course of diphtheria, tetanus, pertussis, polio (DTaP and IPV) vaccine at any time by their fifth birthday as a percentage of all children whose fifith birthday falls within the time period. ## Rationale A booster vaccine for diphtheria, tetanus, pertusiss and polio disease has been in the routine childhood immunisation programme since late 2001. It is currently offered at 3 year and 4 months or soon after. Vaccination coverage is the best indicator of the level of protection a population will have against vaccine preventable communicable diseases. Coverage is closely correlated with levels of disease. Monitoring coverage identifies possible drops in immunity before levels of disease rise. Previous evidence shows that highlighting vaccination programmes encourages improvements in uptake levels. May also have relevance for NICE guidance PH21: Reducing differences in the uptake of immunisations (The guidance aims to increase immunisation uptake among those aged under 19 years from groups where uptake is low). ## Definition of numerator Number of children in LA responsible population whose fifth birthday falls within the time period who received a DTaP and IPV booster at any time before their fifth birthday. ## Definition of denominator Total number of children in LA responsible population whose fifth birthday falls within the time period. Coverage figures are supplied for patients registered with GPs based in that LA and for unregistered patients who were resident in that LA. The LA responsible population is therefore different from the estimated resident population figures produced by the Office of National Statistics (ONS) for each LA. For the COVER collection, the LA responsible population is usually derived from the population registers held on CHISs. ## Caveats Full GP postcodes are used to aggregate data to ICB. The GP-level coverage data is collected by NHS Digital Strategic Data Collection Service (SDCS) and published by the UK Health Security Agency (UKHSA) COVER team. ICB data is experimental and should be treated with caution as it is not an official statistic. Information on childhood immunisation coverage at ages one, two, and five is collected through the UK COVER collection by UKHSA. These aggregated data are collected from CHISs, computerised systems storing clinical records that support health promotion and prevention activities for children, including immunisation. In England, COVER data are collected for Upper Tier Local Authorities (LAs) using the COVER data collection form. These are established collections based on total populations, not samples. The number of CHIS systems has decreased from over 100 in 2015 to around 70 by mid-2017. As different phases of the digital strategy are implemented across the country, it is anticipated that there may be further temporary local data quality issues associated with the transition. Temporary data quality issues in some London COVER returns during 2017 to 2018 were observed in the quarterly COVER reports as the new Hubs became responsible for generating coverage data. Changes in vaccine coverage within London should therefore be interpreted with caution for the time being. Data are extracted directly from local population registers, and data issues are generally related to underestimation of coverage. There may be some overestimation of denominators due to children who have moved away remaining on the area register, which can lead to underestimates of coverage. In some areas, it is known that a small number of GPs do not submit vaccination data to the local CHIS, also resulting in underestimation of coverage. Using non-standardised data extraction methods could result in overestimated coverage. Caution should be exercised when comparing coverage figures over time due to occasional data quality issues reported by some data suppliers. Apparent trends could reflect changes in the quality of data reported as well as real changes in vaccination coverage. While this issue will be more apparent at the local level, it may also impact national figures. Similarly, some caution should be exercised when comparing coverage between different areas where data quality issues have been reported.