Vaccine to stop heart attacks could be here in 5 years

First, there is no causal connection known between cholesterol deposition in arteries and heart disease. There is an absolutely clear correlation between the two, but no evidence of cause and effect whatsoever. Decades back, calcium was attributed with the same causal affect that cholesterol is given now due to the same correlation, and that's resulted in a massive increase in osteoporosis among those who followed the medical advice.

Second, it has been done in mice. There's a few things you need to know about mice in the lab. First, they're inbred. Everyone works in a few, genetically homogeneous strains (typically with a number of serious genetic defects). Typically the results found in one strain change entirely when done in another strain. Laboratories deal with this by only working on one strain and ignoring all the others. Second, the standard care practices throughout the world for lab mice leave them morbidly obese and inactive. All lab mice suffer from metabolic syndrome. Any time you see a result in the literature on obesity, fat buildup, heart disease, diabetes, or any other metabolic issue where the experiments were done on mice, it is more likely that the experiment's treatment made the mice drop some weight and become more metabolically normal than that it had any actual effect.