El-Turki, A;
Long, P;
Wong, ICK;
Smith, H;
(2017)
How valid are IMS DA summary statistics of children's vaccination status?
Pharmacoepidemiology and Drug Safety
, 26
(1)
pp. 108-111.
10.1002/pds.4080.
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Abstract
Purpose: Accurate recording of immunisation status is essential for the evaluation of any immunization program. In September 2006, 7 Valent Pneumococcal Conjugate Vaccination (PCV7) was introduced into the UK’s routine childhood immunisation programme. This study validated the PCV7 immunization status of children aged 2 years recorded in the IMS Disease Analyses database. / Methods: The PCV7 vaccination uptake rate for children born in 2008 in the IMS DA database was calculated. A sample of 173 of the 2497 children not recorded as vaccinated was identified and a questionnaire was sent to each of their General Practitioners to ascertain the child’s true PCV7 vaccination status. / Results: In the IMS DA data of 15,237 children born in 2008, 12,740 (83.6%) had a vaccination record of PCV7. One hundred and eleven of the 167 questionnaires sent to the child’s general practitioners were returned, giving an adjusted response rate of 111/167 (66.5%). Based on the general practitioners’ responses, 71 (64%) of these children were fully vaccinated according to their General Practitioner’s records making the revised estimated vaccination rate for this cohort 94.1%. / Conclusion: This validation study has shown that caution is needed if using historical IMS patient-level data to analyse the effectiveness of PCV7 as there is a potential under-recording of immunization leading to underrepresentation of vaccination rates by approximately ten per cent. Coverage of other vaccines may also be underestimated in the IMS database.
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