We didn’t have so much as a sniffle in our house for 2+ years. Masking, distancing, and not going to restaurants—we just
did not get sick. Even after the kids went back to school—we had them in a school with heavy-duty air filters in every room and high masking compliance, at the time.
Now we’re sick constantly, it seems. It’s so much worse than before. I think our immune systems are doing some catching up.
[edit] for the timing, we started getting sick a bunch right around the time masking dropped off to near-zero everywhere around us.