It looks to me like
Vaccine Man is standing on top of a pile of debris. If Vaccine Man detonated an explosion at his feet then he's not going to be standing on top of a pile of debris, is he?
How would it end up underneath him if he didn't move from the spot he was at when the explosion went off?
So it looks to me that the explosion went off, and then Vaccine Man moved there to stand on top of the debris created by the explosion.
That doesn't imply that. It just means that he made his appearance known with an explosion. Not that he caught himself in the explosion.