October 05, 2012
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Suboptimal response to H1N1 vaccine reported in Down syndrome

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Adjustments to the influenza vaccination schedule may be necessary for children with Down syndrome, although more data are needed in this population of children, according to study findings published online.

Maaike A. Kusters, MD, of the Jeroen Bosch Hospital in the Netherlands, and colleagues reported their data on 48 children, aged 7 months to 17 years, with Down syndrome who received two doses of influenza A/H1N1 vaccine during 2009.

The researchers reported that “92% reached the previously defined protective level — hemagglutination inhibition titer greater than or equal to 1:40 — but only 27% reached the level of greater than or equal to 1:110, which was recently described to predict the conventional 50% clinical protection rate.”

Certain anatomic abnormalities may predispose children with Down syndrome to a blunted response to influenza vaccine and others. The researchers said they urge further research of influenza vaccination with this population of children, and further research into exactly what the established cutoff values should be.

Kusters and colleagues said there has been some debate on the cutoff values that would show correlates of protection. Hemagglutination inhibition titers induced by influenza vaccines are considered correlates of protection, but some published data have shown this is not always true. Therefore, the researchers noted, more data with larger sample sizes are needed into the immune responses that correlate with protection, particularly in the pediatric population.

Disclosure: Kusters reports no relevant financial disclosures.