Children with HIV responded suboptimally to novel adjuvanted influenza A (H1N1) vaccine

VANCOUVER — Less than 70% of children with HIV achieved seroprotection from the AS03-adjuvanted pandemic influenza A (H1N1) vaccine (Arepanrix, GlaxoSmithKline), according to findings presented at the 48th Annual Meeting of the Infectious Diseases Society of America.

Jason C. Brophy, MD, MSc, of the Division of Infectious Diseases in the Department of Pediatrics at Children’s Hospital of Eastern Ontario in Ottawa, and colleagues prospectively assessed vaccine responses in 78 children from two pediatric HIV clinics in Ontario. They performed hemagglutination inhibition titers at baseline and at 8 weeks after vaccination.

Children aged younger than 10 years were administered two intramuscular doses of .25 mL vaccine on days 0 and 21. Children aged older than 10 years received a single full dose at .5 mL intramuscularly.

Primary endpoints were defined as seroprotection with a hemagglutination inhibition titer ratio of >1:40 and seroconversion with a >fourfold rise in titer to >1:40.

Median baseline characteristics indicated that children were aged 13.2 years (IQR 9.1–15.6; 33% <10 years) with CD4 counts of 659 cells/mm³ (IQR 487–1,090) and viral loads of <50 copies/mL (IQR <50–1,120). Sixteen children were not receiving ART.

Previously-defined hemagglutination inhibition titer seroprotection criteria were met by 69% of the children at 8 weeks. The seroconversion rate was 43% at the same time point.

“This fails to meet European Union Committee for Medicinal Products for Human Use seroprotection criteria of 70%,” Brophy said in the presentation.

However, Brophy noted that these levels were maintained over six months. “We saw a 68% seroprotection rate and a 37% seroconversion rate by that point.”

Brophy noted that in the univariate analysis, viral load was the only factor significantly associated with seroprotection (P=.07). “Use of ART, site and CD4 counts at baseline were not significant predictors,” he said.

Multivariate analysis results indicated that viral load (P=0.009) and CD4 count (P=0.03) were the strongest predictors of seroprotection. “Viral load continued to be the only significant predictor of seroconversion in the multivariate analysis, with a P-value of .003,” Brophy said.

Mild vaccine–related adverse events were observed in 85% of children. The most commonly reported adverse event was injection site pain, which was observed in 65% of children. There were no serious adverse events reported.

“The rates we observed were very similar to rates seen in other types of seasonal influenza vaccines done in children with HIV,” Brophy concluded. “The AS03-adjuvanted H1N1 vaccine yielded substantially lower rates of seroprotection and seroconversion in children with HIV compared with healthy children.” – by Rob Volansky

For more information:

Brophy JC. #176.Immunogenicity of AS03-Adjuvanted H1N1 Pandemic Influenza Vaccine in HIV-Infected Children. Presented at: the IDSA 48th Annual Meeting. Oct. 21-24, 2010; Vancouver, B.C.

Disclosure: Brophy reported being a grantee in an unrelated investigator-driven project at Abbott.

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