You've made an amazing claim, that infected healthcare workers, who, were caring for Covid patients for almost 2 years now, have been spreading COVID further.

You've made an amazing claim, that infected healthcare workers, who, were caring for Covid patients for almost 2 years now, have been spreading COVID further. This, despite the fact that they are most likely to have caught it early as they were caring for patients prior to vaccines, and hence to have obtained natural immunity. Please provide evidence to support your amazing claim.