Centre-back Vlaar forced his way into the preliminary squad after an impressive season with Feyenoord but was unable to seal a place in the final party.
Midfielder Lens was a surprise inclusion in the original squad and Van Marwijk has opted to take Babel instead.
PSV Eindhoven forward Otman Bakkal and midfielders Wout Brama (FC Twente) and David Mendes Da Silva (AZ Alkmaar) were all omitted from an original 30-man squad 10 days ago.
Former Manchester United striker Ruud van Nistelrooy was not considered.
The Dutch, who have yet to win the World Cup despite reaching two finals in 1974 and 1978, have been drawn in Group E alongside Denmark, Japan and Cameroon.
They are due to play friendlies against Ghana (1 June) and Hungary (5 June).
Squad: Maarten Stekelenburg (Ajax), Sander Boschker (FC Twente), Michel Vorm (FC Utrecht); Khalid Boulahrouz (Stuttgart), Edson Braafheid (Celtic), Giovanni van Bronckhorst (Feyenoord), John Heitinga (Everton), Joris Mathijsen (HSV), Gregory van der Wiel (Ajax), Andre Ooijer (PSV); Mark van Bommel (Bayern Munich), Nigel de Jong (Manchester City), Stijn Schaars (AZ), Wesley Sneijder (Inter), Rafael van der Vaart (Real Madrid), Demy de Zeeuw (Ajax), Ibrahim Afellay (PSV); Dirk Kuyt (Liverpool), Eljero Elia (HSV), Ryan Babel (Liverpool), Klaas-Jan Huntelaar (AC Milan), Robin van Persie (Arsenal), Arjen Robben (Bayern Munich).
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