Cause cancer is just a word we use to refer to over a hundred different diseases with often unknown causes. Several forms can be cured already, and because it’s second cause of death for humans (600K per year in just the US), it’s rushed as much as possible.
Rushed does not equal too hasty though. If covid vaccine development would be spread out over a decade or more, they’d do no more or less work than has been done now.
Besides that, sorry to break it to the anti-vaxxers, there will indirectly be mandatory vaccination in pretty much every country in the world, especially if you travel, have child in day care, want to go to large events, join on orgy, etc etc. It’ll be tested some more on the old and the weak anyway before it’s my turn. Which won’t be the case for probably another 6 months at least. UK starts this month. If they don’t turn into zombies before next summer, I’ll get vaccinated asap and party like it’s 2019. I’ll be hugging strangers all over the planet, drunk, high and sleep-deprived. Summer of Love, 2021 edition.