All of the real world data could be just coincidental. We had a steep drop off last summer only to surge again in winter. Right now we are heading to summer and see a steep drop off but they claim it’s due to vaccines. Maybe it is. The trial data suggests the vaccines reduce risk greatly. But it seems most of the new cases even now are happening in the states up north where they say that, due to the earth’s angle facing the sun, there isn’t enough sun exposure to enable the body to produce enough vitamin D far north - north of the 40th degree parallel.
Doesn’t explain Italy, though, so there is contrary evidence to examine.
Just data to throw into the mix. I don’t have the answers, just some clues to follow. FWIW, much of Europe suffers the same because they are also far north.
I don’t believe in coincidence much. Most folks north if the 35th don’t get enough vitamin D, which is a critical part of staying healthy.