"Vampirology" is fluid. In Dracula, the Count could not enter a home unless invited. Nor could he even cross over the threshold of his own domains - he would have to leave by crawling out a window and scamper down the walls like a spider. Of course, Bram Stoker broke these rules throughout his novel. In 'Salem's Lot, the vampires could not enter a home without being invited. Of course, Stephen King broke this role a few times.
In other vampire works, whether written or filmed, the rules of invitation were completely ignored. It all depends upon the intent of the creators. In the Hammer films, Christopher Lee could use his supernatural strength to break through any door or window to feast on whatever nubile pretty thing was beyond. In The Last Man on Earth, the best cinematic adaptation of Richard Matheson's I Am Legend, the vampires (created by a virus) were individually weak, and sometimes mob weak, unable to break through a locked or barricaded door or window.
Gerard