Obama did commit a minor gaffe by claiming that the science is inconclusive. It wasn’t at the time, but those weren’t prepared remarks, and for all we know, Obama might have meant to say that those alleged studies were inconclusive. He also immediately said that the vaccination system on the whole is OK, and later clarified his position to leave no doubt that he supports vaccination.
Even if Vox wanted to interpret it as “pandering” (and there’s no evidence that it was), Vox is dishonest to omit the fact that “this person” wasn’t Obama and that Obama supported vaccination when asked directly.