Varicella is still around despite the vaccine—and in some cases it can still be fatal, according to the Centers for Disease Control and Prevention.
Varicella vaccination is more than 95% effective against severe disease, and, since 1996, has been recommended for routine administration to children aged 12–18 months and to all susceptible persons aged 13 years and older. For children aged 19–35 months, national estimates of varicella vaccine coverage increased from 26% in 1997 to 85% in 2003, resulting in substantial reductions in varicella morbidity and mortality.
In two Varicella Active Surveillance Project sites—Antelope Valley, Calif., and West Philadelphia, Pa.—the number of reported cases dropped by approximately 85% during 1995–2003, and hospitalizations by about 70%.
Yet, cases are still occurring among both vaccinated and unvaccinated individuals, as are a small number of varicella-related deaths among those not vaccinated or whose vaccination status is unknown, the CDC said in two separate reports (MMWR 2005;54:272–6).
During 2003 and the first half of 2004, the CDC received reports of eight varicella-related deaths, of whom six were unvaccinated and vaccine status unknown for the other two. The decedents ranged from 1 to 40 years, including six children and adolescents younger than 20 years of age. Three of the children had preexisting immunosuppressive conditions.
The other three, all initially healthy, were a 12-year-old boy, a 10-year-old girl, and a 14-month-old girl. None had been vaccinated or previously had the disease. Two had been exposed to classmates with varicella, while the source for the third child was unknown. All three had been brought to the emergency room with rashes consistent with varicella.
The 12-year-old was having repetitive episodes of vomiting, shortness of breath, and weakness. He was afebrile and initially had a 97% pulse oximetry, which dropped to 69% after he was hospitalized. He died on the second hospital day after having a seizure and becoming apneic. The 10-year-old died on the fourth hospital day after hospitalization for fever, ataxia, and changes in mental status.
The third child was brought to the hospital with vomiting, diarrhea, fever, and reduced oral intake 3 days after her rash appeared. She became hypotensive and was diagnosed with varicella and septic shock. Despite fluid resuscitation, intravenous ceftriaxone, vancomycin, and acetaminophen and transfer to a children's hospital, she developed respiratory and cardiac arrest and died less than an hour after arriving, the CDC reported.
To prevent varicella from occurring among children in the age range of the older two who died, middle- and high-school entry vaccination requirements will be necessary. By June 2004, a total of 44 states had implemented child care and/or school entry requirements for varicella vaccination. However, as of March 2005, only 18 states had included middle- or high-school entry requirements, the CDC said.
In Oregon, which has requirements for vaccination prior to out-of-home child care, kindergarten, and seventh grade, the Multnomah County school district has been conducting surveillance since the 2002–2003 school year for 37,850 students in 109 public elementary schools in kindergarten through fifth grade (5–10 years old).
Overall for the 2002–2003 and 2003–2004 school years, approximately 60% of varicella cases occurred as a single case in classrooms, while 40% were part of classroom outbreaks (defined as two or more cases within 21 days). Twenty-two percent were among students aged 7 years, while 19% occurred in 6-year-olds. Overall, 69% with varicella had been vaccinated, and 28% lacked evidence of immunity, having neither a history of vaccination nor of disease. Information was missing for the other 3%.
This school-based surveillance method detected more cases than physician-based surveillance alone would have. School nurses reported 90% of new varicella cases, with 88% subsequently confirmed by physicians, nurses, or parents. However, only 34% of the 2002–2003 cases and 44% of the 2003–2004 cases had been initially diagnosed by physicians, according to the CDC.