England had beaten Samoa on their way to the Wellington Sevens title last month, but on the opening night they had few answers as their opponents built up a 21-0 half-time lead with tries from Faatoina Autagavaia (two) and Reupena Lavasa.
Tulolo Tulolo added a fourth try midway through the second half before replacement half-back Sam Edgerley got England's consolation score late on.
England take on Scotland and Portugal on Saturday, with the latter winning their opening game 27-21.
Duarte Moreira's first-half hat-trick and a Goncalo Foro effort saw the Scots trail 20-7 at one stage.
Andrew Turnbull's second try and one from Mark Robertson put Scotland 21-20 ahead before Moreira grabbed a fourth try of his own after the hooter.
Wales needed a late score from Cardiff Blues centre Cory Allen to see off Australia 19-14 in their opening Pool A match.
Argentina were responsible for the shock of the day when they hammered South Africa 21-0.
New Zealand were not affected by the absence of injured world player of the year Tomasi Cama as they saw off France 33-12 in Pool B.