Just tossing this out here as a PSA, dogs can still get kennel cough even after being vaccinated. It’s like the flu vaccine in humans - sometimes the strain that goes around isn’t the one vaccinated for. I had two dogs end up with it and both were fully current on all vaccines. They got it from daycare where an outbreak occurred and our older dog brought it home to the puppy. All dogs there are required to show proof of current vaccines to go so it was just an unfortunate year for the vaccine. Fortunately my dogs got over it with meds and rest for a couple of weeks. Sorry about your sisters dog, that’s heartbreaking.