We take very good care of your personal data and do not pass it on. The app uses your date of birth to calculate some of the vaccine recommendations. If you have stated that you were fully immunised in the UK as a child then we know that you are covered for diphtheria, tetanus and polio until at least aged 23. If you were born before 1970 then it is very likely that you were exposed to measles as a child and so MMR vaccination would not usually be recommended. If you give us an inaccurate date of birth then these calculations will be incorrect.