Chickenpox killed at least eight adults and children in the United States in 2003 and 2004 combined, despite the availability of a safe and effective vaccine, the Centers for Disease Control and Prevention reported on Thursday.

The CDC described the cases of three of the victims - a 12-year-old boy, a 10-year-old girl and a 14-month-old baby - to highlight the fact that the virus can kill even older, robust children despite its reputation as a benign childhood disease.

“The findings in this report underscore the importance of timely routine vaccination of children aged 12 to 18 months and catch-up vaccination of older susceptible children and adolescents according to current recommendations and the need for timely and complete national varicella (chickenpox) death surveillance,” the CDC said in its weekly report on sickness and death.

The three detailed cases, from Arizona, Arkansas, and New York City, involved previously healthy children who had not been vaccinated.

Three others who died had immune system compromises that made them vulnerable to infection.

“Varicella vaccination is more than 95 percent effective against severe disease and, since 1996, has been recommended for routine administration to children aged 12 to 18 months and to all susceptible persons aged more than 13 years,” the CDC said.

Chickenpox, caused by the herpes varicella zoster virus, causes an intensely itchy rash and was once a hallmark childhood disease. The virus often stays in the body for decades to re-emerge in adulthood as a painful condition called shingles.