Taking a cue from the Dogs of the Dow strategy, let's see if any of the Dow's weakest performers in January are worth buying today. Johnson & Johnson (NYSE: JNJ) is as stable of a blue chip stock as they come, but the healthcare giant faced several negative headlines in January that pushed its shares lower, and its earnings report failed to impress the market. Along with partners, it also canceled its phase 3 Mosaico clinical HIV vaccine trial, because the drug was not effective in preventing HIV infection.