True, the Emirates Clinic will not cover what you opt out of initially, likewise with dental treatment. However some countries in Africa and South America require mandatory Yellow Fever vaccinations. For Aircrew and EK staff at those stations, you will need it. Of course it is your right to refuse any vaccination but this may affect your job so ask EK about it if you are having any interview or even before, just email them. Or better still, just take the jabs and get on with life!