Andrew started at 5 months and didn't get sick for quite a while. Josh was 16 months when he started and didn't get sick for months and he started DC in the middle of Winter in Waiouru.
I have seen something that says when you start something new for the first time you usually get sick often. Be that children starting DC, starting a new full time job. It happened with me when I started working full time for the first time I was sick quite often in the first 6 months I was there.