質問: how do you say this in english (us)? このイベントの参加者が、あと5人足りない。 how do you say this in english (us)? このイベントの参加者が、あと5人足りない。
回答: we still need to recruit 5 people for this event / we still need 5 people for this event / we still lack 5 people for this event / we need 5 more people to participate in this event.