The immunogenicity of a novel A (H1N1) vaccine in HIV-infected children
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Updated: May 31, 2026
An Optimized Hemagglutination Inhibition (HI) Assay to Quantify Influenza-specific Antibody Titers
Published on: December 1, 2017
Ifeanyichukwu O Okike1, Chee Yung, Shamez Ladhani
1Vaccine Institute, St. George's, University of London, London, United Kingdom. iokike@sgul.ac.uk
Insights
The AS03(B)-adjuvanted Influenza A (H1N1) vaccine demonstrated high immunogenicity in HIV-infected children, with 94% achieving seroprotection. Vaccination did not significantly impact CD4 counts or viral load in this vulnerable population.
Area of Science:
- Pediatric Infectious Diseases
- Immunology
- Virology
Background:
- In 2009, the UK Department of Health recommended the AS03(B)-adjuvanted Influenza A (H1N1) vaccine (Pandemrix) for high-risk groups, including children with HIV.
- No prior data existed on the vaccine's immunogenicity in this specific pediatric population.
Purpose of the Study:
- To evaluate the immunogenicity of the adjuvanted Influenza A (H1N1) vaccine in HIV-infected children.
- To assess the vaccine's impact on CD4+ T cell counts and HIV viral loads.
Main Methods:
- 31 HIV-infected children received two doses of the H1N1 vaccine, 3 weeks apart.
- Serum antibody responses were measured using a haemagglutination inhibition (HAI) assay before and after vaccination.
- CD4+ T cell counts and HIV viral loads were monitored.
Main Results:
- 94% of vaccinated children achieved seroprotection (HAI titres ≥ 1:32) after two doses.
- 87.1% demonstrated seroconversion (a four-fold rise in titres).
- No significant changes in CD4+ T cell counts or HIV viral loads were observed post-vaccination.
Conclusions:
- The AS03(B)-adjuvanted pandemic Influenza A (H1N1) vaccine is highly immunogenic in HIV-infected children.
- The vaccine appears safe for this population, with no adverse effects on immunological markers.
Background:
In October 2009, the United Kingdom Department of Health recommended vaccination of high-risk groups, including children with HIV, with a novel, oil-in-water AS03(B) adjuvanted Influenza A (H1N1) vaccine (Pandemrix). There were no published data available regarding the immunogenicity of this vaccine in such children.
Objectives:
This study evaluated the immunogenicity of the adjuvanted Influenza A (H1N1) vaccine in HIV-infected children immunised according to national recommendations and assessed the impact of vaccination on individual CD4 counts and HIV viral loads.
Methods:
HIV-infected children attending outpatient appointments between 01 November and 31 December 2009 were offered two doses of H1N1 vaccine three weeks apart and a blood test before and 3 weeks after the second dose of vaccine. Serum antibody responses were determined by a haemagglutination inhibition (HAI) assay using standard methods.
Results:
Of the 39 children recruited for vaccination, 31 (median age 11.2, range 3.0-17.9 years) received both doses of vaccine and provided pre- and post-vaccination blood samples. Eight children (26%) had baseline HAI titres ≥ 1:32. After vaccination, 29 children (94%, 95% CI, 78.6-99.2%) had HAI titres ≥ 1:32 (seroprotection), of whom 27 (87.1%, 95% CI, 70.1-96.4%) had also had a four-fold rise in titres (seroconversion). In the univariate analysis, post-vaccination geometric mean titres (GMTs) were higher among the 21 children receiving highly active anti-retroviral therapy compared with the 10 treatment-naïve children (GMT 406 [95% CI 218-757] vs. 128 [49-336]; P=0.035), but this was no longer statistically significant when adjusted for prevaccine GMTs. There was no significant impact of vaccination on CD4+ T cell count or HIV viral load.
Conclusion:
The AS03(B)-adjuvanted pandemic Influenza A (H1N1) vaccine is highly immunogenic and appears to be safe in HIV-infected children.
