... if he was really vaccinated the first time, he wouldn't need to be vaccinated "again". I have no idea why this place would stage a vaccination, but they clearly did. Maybe it was for some innocuous (heh heh heh) reason. Whatever the reason and intent, it damages their credibility and the credibility of the people desperately pushing a vaccine for a disease most people barely notice.
And speaking of lost credibility, note that they aren't going to broadcast their volunteers' second sticking, just promise that he got one without showing any proof.
For a good roundup of potential problems with the vaccine, see here. While these are all in the realm of potential problems (with the exception of possible fertility issues, for which there is evidence in similar viruses, making is more than just speculative), the insane rush towards applying this vaccine to everyone makes my risk-management antenna twitch like mad.