Here's a good example. Global Warming, most of us know it exists, but 97% of scientist believe it does, so that 3 percent it's easy for doubters to find holes in any logical statistic, etc.
They can easily find a scientist and cite them to push their point. Very similar for covid vaccine, but easier to cast doubt on because lack of data, because there isnt additional data on effects years down the line because the virus is obviously new
But we can see what has been done and the trials that were run as just an example and go off that. We can now see data from millions of people that have taken it, and the rarety these effects have etc