An EMT reaches the scene of a car accident, disinfecting and dressing a man's head wound that has been bleeding profusely. Upon taking off his bloodied latex gloves, he notices that a shard of window glass has penetrated one glove and cut is palm. Years later, long retired after a second career as an accountant, he is surprised to discover that he has liver cancer. Thinking back, he recalls having received both hepatitis vaccines available at the time of the exposure, and guesses that he may most likely have been exposed to .