In the interest of not accelerating the flame war, I am not addressing this to any specific person.
The Covid-19 vaccines are designed to stimulate immunity to the virus. The immune system is not an all-or-nothing deal - it has many different components and of course every person's is slightly different. One of the things it can do (and usually does, that being its proper function) is to reduce viral load (a subject familiar to most members of this site) and thereby the chance of transmission. Therefore, the Covid-19 vaccines (more than one, remember) are expected to reduce the overall rate of transmission. There is evidence that suggests that in fact they do.
[think before following links] https://www.cidrap.umn.edu/news-perspective/2021/08/study-ties-covid-vaccines-lower-transmission-rates
That said, the management of Crew Club has the right to make whatever decision they see fit regarding the requirement for proof of vaccine, or mask use, or any other damn thing. I strongly suspect that their motivation is to stay open (having just spent over a year with no revenue!), and those of us who enjoy having a sex club to go to in DC would be well advised to support them in that goal, don't you think?