If a vaccine is 90% effective then one in ten who would catch it without a vaccine will still get it, although likely less severely, so its not surprising that vaccinated people have tested positive. Vaccines may also be slightly less effective at preventing transmission. The good news is that they will reduce the 'R' rate to a level where outbreaks will fizzle out automatically. The bad news is that this will not happen until most people have received their shots so not until the end of the year and even then its likely to be extended travel bubbles between countries where the programme has been completed. There may be restrictions to 'developing countries' for some time to come.