Safety with vacuum packed food
Yes, it is. The important part, for nearly any dish, is to heat it properly.

Meat is mainly spoiled by bacteria, worms and larvae. Proper heating solves these problems. Bacteria and mold digest proteins and might generate harmful molecules; while heating does not eliminate them, they are easy to smell, especially those in meat. You won't want to eat it way before it becomes a health risk. The other health risks are unhealthy proteins, like the mad cow disease, hormones and antibiotics. They are stable to heating - but they don't propagate, so if they are in there, then they are in there the moment you purchased them.

Note that fat oxidation/rancidity are not actually health risks, even though they will ruin the taste. But 4 hours is way too short to make any fat rancid.