June 15, 2007

Children with sickle cell get extra vaccine benefit

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Natasha Halasa, M.D., and colleagues found that a childhood vaccine is helping prevent serious pneumococcal infections in children with sickle cell disease. (photo by Susan Urmy)

Children with sickle cell get extra vaccine benefit

A childhood vaccine known to protect against the bacteria that causes ear infections and pneumonia may well be a lifesaver for children with sickle cell disease.

Researchers at the Monroe Carell Jr. Children's Hospital at Vanderbilt and colleagues at other institutions found that pneumococcal conjugate vaccine (PCV), known commercially as Prevnar, reduced serious pneumococcal infections by 93 percent in children younger than age 5 who have sickle cell disease.

Their study appears in the June issue of Clinical Infectious Diseases.

“Invasive pneumococcal disease (IPD) affects children with sickle cell disease at 30 to 600 times the rate of children without sickle cell disease,” said principal author Natasha Halasa, M.D., assistant professor of Pediatric Infectious Diseases. “We looked at TennCare records across the state and linked it to a database that tracks IPD and found that children with sickle cell disease younger than age 5 had high rates of IPD before Prevnar was introduced, with a 5.4 percent mortality rate. In fact, IPD has been reported as a leading cause of death for children with sickle cell disease.”

Prevnar, introduced in 2000, is a vaccine that contains seven serotypes of Streptococcus pneumoniae that most commonly cause IPD. It is recommended for all children under 2 as well as children age 2 to 4 at high risk for IPD, including those with sickle cell disease. The study found that broad use of Prevnar was a clear turning point for children with sickle cell disease.

“When you look at cases of IPD in these children after the introduction of the vaccine, the rates dropped more than 90 percent in those with sickle cell disease under the age of 5,” said Halasa.

“Our population was small, but we had no deaths in the four years after Prevnar was introduced.”

Before the vaccine's introduction, daily penicillin prophylaxis was the standard treatment to prevent serious illness from pneumococcal disease in children with sickle cell disease. And while that worked — reducing the rate of IPD by more than 80 percent — it can be difficult for many families to fully comply with the antibiotic prevention regimen.

In addition, many of the serotypes that caused IPD have become resistant to penicillin.

Vanderbilt researchers are optimistic about the vaccine, but cautiously so.

“The major concern is that other pneumococcal serotypes not covered by the current vaccine will become more common, and that pneumococcal diseases will begin to increase again,” said Marie Griffin, M.D., professor of Preventive Medicine and senior author of the study.

“That is why it is very important to continue to monitor the effects of the current vaccination program and support efforts to develop new vaccines. Physicians should be cautious about their hopes that Prevnar vaccine brings the risk to these children to an end.”

Other contributors to the study were Vanderbilt's Sadhna Shankar, M.D.; Tom Talbot, M.D.; Patrick Arbogast, P.h.D.; William Schaffner, M.D.; Ed Mitchell, M.D., with Preventive Medicine; and Winfred Wang, M.D.