Launchbury sustained a knock in England's final warm-up fixture against Italy, while head coach Eddie Jones was without Slade for all of the preparation games as the centre recovered from a knee injury.
However, the duo will be able to take part in England's World Cup opener against Tonga on September 22, meaning Jones will have 29 of his 31-man squad available for selection.
Mako Vunipola and Jack Nowell will still be missing, with both players expected to be out for at least the first two pool-stage matches.