A vaccine introduced in 2000 has reduced by more than 90 percent the rate of a serious bacterial illness among young children with sickle cell disease (SCD), who are particularly susceptible to it, according to a new study that appears in the June 1 issue of Clinical Infectious Diseases.
SCD is an inherited blood disorder that affects red blood cells, sometimes turning these cells crescent-shaped. The deformed cells can get stuck in small blood vessels, creating blockages that can reduce blood flow. SCD can cause painful episodes and strokes, and can damage organs including the lungs, kidneys, liver, and spleen. The average life expectancy of someone with SCD is in the mid-40s. In the United States, it is estimated that more than 70,000 people are living with SCD and about 1,000 babies are born with this condition each year.
Diseases caused by a bacterium known as pneumococcus are a leading cause of death among children with SCD. People with SCD are between 30 and 600 times more likely to develop pneumococcal meningitis, bloodstream infections, and other serious infections, compared to individuals of comparable age and race without SCD.
The new study, by Natasha Halasa, MD, MPH, of Vanderbilt University's School of Medicine and colleagues, looked at pneumococcal disease rates among young children with SCD in Tennessee's Medicaid program before and after the introduction in 2000 of the pneumococcal conjugate vaccine (PCV). They found the rate of serious pneumococcal disease dropped by more than 90 percent among children under 5 years of age.
"I was not surprised that there was a decrease," Dr. Halasa said, "just surprised about the magnitude of the decrease."
Since its introduction in 2000, PCV has been recommended for all children younger than 2 years of age, and for selected children 2 to 4 years with certain high-risk conditions, including SCD. The authors write: "With the universal administration of PCV to all children, both with and without SCD, it is expected that the rates of invasive pneumococcal disease (IPD) will continue to decline in all children."
Dr. Halasa did express concern, however, that other strains of pneumococcus besides the seven included in the vaccine might become more common, thus renewing the threat of IPD. For this reason, she said, monitoring for IPD should continue in all populations, including those who are at high-risk for IPD, such as those with SCD or HIV.
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