How many people have achieved the Triple Crown of Acting, a term used in the American entertainment industry to describe actors who have won a competitive Oscar, an Emmy Award, and a Tony Award in the acting categories?

Triple Crown of Acting - Emmy + Oscar + Tony in ACTING categories

TCA WINNERS
1. Helen Hayes (1953)
2. Thomas Mitchell (1953)
3. Ingrid Bergman (1960)
4. Shirley Booth (1962)
5. Melvyn Douglas (1968)
6. Paul Scofield (1969)
7. Jack Albertson (1975)
8. Rita Moreno (1977)
9. Maureen Stapleton (1982)
10. Jason Robards (1988)
11. Jessica Tandy (1990)
12. Jeremy Irons (1997)
13. Anne Bancroft (1999)
14. Vanessa Redgrave (2003)
15. Maggie Smith (2003)
16. Al Pacino (2004)
17. Geoffrey Rush (2009)
18. Ellen Burstyn (2009)
19. Christopher Plummer (2012)
20. Helen Mirren (2015)
21. Frances McDormand (2015)
22. Jessica Lange (2016)
23. Viola Davis (2017)
24. Glenda Jackson (2018)

https://www.goldderby.com/forum/movies/egottriple-crown-of-acting-watch-who-can-join-next/

Additionally, there is also a British version of the Triple Crown of Acting. Helen Mirren is the only one to have completed both the American and British Triple Crowns.
https://en.wikipedia.org/wiki/Helen_Mirren

There is also the quadruple crown which is
Emmy + Grammy + Oscar + Tony

Name
1. Richard Rodgers
2. Helen Hayes
3. Rita Moreno
4. John Gielgud
5. Audrey Hepburn
6. Marvin Hamlisch
7. Jonathan Tunick
8. Mel Brooks
9. Mike Nichols
10. Whoopi Goldberg
11. Scott Rudin
12. Robert Lopez
13. Andrew Lloyd Webber
14. Tim Rice
15. John Legend
16. Alan Menken

https://en.wikipedia.org/wiki/List_of_EGOT_winners