A securing device for transport of a neonatal patient in a temperature-controlled incubator comprises a vacuum mattress (12), comprising a gas-tight mattress case (14) enclosing a granular filler material (16), which vacuum mattress (12) is arranged to be brought from a flexible state into a rigid state by evacuation of gas from the same, the vacuum mattress (12) comprising a first side portion (28) arranged to be folded up around a first side of the patient (22), a second side portion (30) arranged to be folded up around a second side of the patient (22), and a bottom portion (27) arranged to be fastened in an incubator (48).