"Highly annoyed" could be an understatement related to past "political" discussions here of coronavirus (but I'm not suggesting at all that Fork boy was doing anything other than asking a reasonable question. To partially answer that question -- I do know a person with CH, on the D3 regimen and using Benadryl in cycle, who contracted Covid).
But just in terms of people with CH and disease, Rozen's study of 1,134 people with CH, conducted in 2008 through surveys of people here and at CH.com, had two very interesting findings. Considering that there is a strong prevalence of smoking (and often heavy smoking) among people with CH, there were only three reported cases of lung cancer among the 1,134 survey respondents (the CDC estimates that 10-20 percent of smokers develop lung cancer), and "cluster headache is associated with a low prevalence of cardiac disease as well as cerebrovascular disease, even though the majority of CH patients are chronic heavy smokers."
This was long enough ago that that it's unlikely that more than a very small percentage of the respondents had been either doing the D3 regimen or using diphenhydramine. Could be just statistical anomalies, of course, but could also be that just having CH somehow provides some kind of protection against some conditions, in ways that no one really understands.