
Jackson capitalised on poor defending to find the net in the fourth minute when he sped down the wing, cut inside unchallenged and drilled a shot under Alphonse Areola.
Fourteen minutes later the Senegal striker found space between West Ham’s defenders to receive a pass from Moises Caicedo and double Chelsea’s lead.
West Ham were 3-0 down little more than a minute into the second half when Jackson teed up Cole Palmer on the break and the England striker fired home from the edge of the box.
Chelsea, who won 1-0 at Bournemouth last Saturday, moved into second place in the Premier League table ahead of the rest of the weekend’s fixtures.
West Ham, under new coach Julen Lopetegui, are 14th.