Vaccination details are collected on the CHL ("Child Health") form. The version of the form used using DS Rounds 1 - 16 (i.e. until mid-2007) is shown below. A cosmetically prettier, but otherwise identical form was used in Rounds 17 and 18 (i.e. Jul 2007 - Jun 2008). From July 2008 a heavily revised version of the form, also included below, has been used.It was updated for 2010 to record several new vaccinations. Until Round 18 the CHL form was an ad-hoc form (i.e. not pre-printed, and the trigger for a fieldworker to complete one was a prompt on the HMU form asking "Has [NAME] turned 1 since last visit?" From Round 19 a pre-printed CHL is included in the bundle for every resident child aged 1-4. In other words the CHL is now typically administered several times, not just once as before. The pre-printed CHL contains details of all vaccinations recorded in earlier Rounds so will only require addition of new vaccinations. In this way the quality of data should be greatly improved as data is collected much closer to the event - and also many fewer children should escape the net entirely. Most of the Vaccinations dates are held in the database only as "Variable precision dates" i.e. text strings which may be precise e.g. 20041223 or have, perhaps, an unknown day e.g. 200412UU. The dates offered in this dataset are „real? dates where the UU values have been randomly assigned. This is done each time the dataset is extracted, and so may vary from one analytical dataset copy to another.
