My training is that Varicella is no longer contagious once a full five 24-hour periods have passed from the onset of the first lesions. The Red Book states, "...may return to school on the sixth day after the onset of the rash...other children with a prolonged course should be excluded for the duration of the vesicular eruption." What's the longest duration of true, fluid-filled blisters the providers out there have seen? Today I saw a child with a severe case who's eight days out and still seems to be developing new tiny lesions in addition to having a handful of un-crusted vesicles. Incidentally, isn't it kind of stupid for schools to still be excluding kids with chicken pox? By now, either a child has been vaccinated or the parents have refused the vaccine, which is their way of stating that they have made an active decision that they want their child to contract the natural disease. This child's mother declined the vaccine at the four, five, and six year visits and had decided she would give it to him at his upcoming seven year visit. Interestingly, they traced the classroom outbreak to a child with shingles who was continuously scratching (and of course spreading the virus around), and the child who reportedly developed the worse case of Varicella was a child who had received the vaccine. Michael Sachs, M.D. General Pediatrician