I'm not implying these vaccines are unsafe at all, but when you're vaccinating close to the entire world' population (eventually), a side effect of 1 death for every 50,000 people vaccinated, might not be seen in a trial of 15,000. But vaccinate 6B people and that's 120,000 dead. So your vaccine can go from "safe" to "it kills people" pretty quick when you're treating millions of people.
Edit: And sure, Covid has killed more than 120,000, but what do you think will happen when people find out the vaccine kills people? They won't care it's 1 in 50,000, they'll just refuse any and all vaccines. Then what?
That's true. But currently just a fraction of global population got infected and already 1.3 million people died. I still think though they shouldn't rush and do enough research because any bad side effects would have long term effect for any other future vaccine treatments.
Edit: And sure, Covid has killed more than 120,000, but what do you think will happen when people find out the vaccine kills people? They won't care it's 1 in 50,000, they'll just refuse any and all vaccines. Then what?