Letter: Continue smallpox vaccination.
D001208:Asia; D004196:Disease Outbreaks; D005060:Europe; D006801:Humans; D007109:Immunity; D012899:Smallpox / Q000453:epidemiology / Q000276:immunology / Q000517:prevention & control*; D014481:United States; D014492:United States Public Health Service; D014611:Vaccination