Again, this is not a WHO approved course of action. But the aggregate of the information suggests that it is a viable stopgap measure. Just highlighting one report:
https://onlinelibrary.wiley.com/doi/10.1111/all.14584
We would like to report here on our clinical observations in 255 subjects, vaccinated in our Center since the start of the Coronavirus disease‐2019 (COVID‐19) pandemic, with the mumps‐measles‐rubella (MMR) vaccine and of whom thirty‐six have presented COVID‐19, all with a remarkably mild course.
The cases in question had zero hospitalization. Similar story to the sailors on the USS Roosevelt, but this group were not healthy servicemen, they were comorbidity ridden civilians, with all kinds of issues including asthma! That is obviously even more unlikely to happen without a medical effect from the vaccine. So now we're going to speculate.
This is what the data from these studies shows
No MMR immunity------------ severe Covid can occur
Old MMR dose------ low titres----- possible severe Covid, worse as titres drop
Recent MMR ---------------- 95-100% observed
mild cases only.
So we have some cross immunity, maybe by T cells, maybe by antibodies and the mumps ones seem implicated, which makes no sense as that's a paramyxovirus, different to SARS-Cov-2. What this translates to is faster killing of the virus as it starts to replicate, with a lower number of dead virus matter. Hence, we get less cytokine storm, or none at all. Wish I'd found this collection of data earlier. I'm starting vaccination on selected high risk patients that I know.
This may not be suitable for you, as you may live in a place where the approved vaccines will soon become available. And that is better than a non-established but high potential stopgap. If you are interested you could send the link world.org to your doctor, and talk it over.