Wasn’t it Trump who said their would be a vaccine by November? Looks like he was right... Hmm!
Their: Shows ownership by multiple people Ex: it is THEIR house.
They’re a contraction for they are. Ex. They’re a bunch of idiots.
There: In this case it is the correct word to use since the subject of the sentence follows the verb. Verb = “said”, Subject = vaccine. EX: Said there would be a vaccine.
Snopes would probably tag that as false. The President said there would be one by election day, and so pfizer held off on the news until 5 days after. See? The President lied, they would say.