A(H1N1)pdm09 Vaccination of Health Care Workers: Improved Immune Responses in Low Responders Following Revaccination

• Published in: The Journal of infectious diseases Vol. 206; no. 11; pp. 1660 - 1669
• Main Authors: Pathirana, Rishi Delan, Bredholt, Geir, Akselsen, Per Espen, Pedersen, Gabriel Kristian, Cox, Rebecca Jane
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 01.12.2012
• Subjects: Antibodies; Antibodies, Viral - blood; Antibodies, Viral - immunology; Antibody formation; B lymphocytes; Biological and medical sciences; CD4-Positive T-Lymphocytes; Cytokines; Cytokines - genetics; Cytokines - metabolism; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation - immunology; Hemagglutination Inhibition Tests; Humans; Immunity, Humoral; Immunization, Secondary; Immunoglobulin G - blood; Infectious diseases; Influenza A Virus, H1N1 Subtype - immunology; Influenza vaccines; Influenza Vaccines - administration & dosage; Influenza Vaccines - immunology; Influenza, Human - prevention & control; Medical sciences; Memory; Microbiology; Pandemics; T lymphocytes; Vaccination; Viruses; Infection; Influenzavirus A(H1N1); Immune response; Vaccination
• ISSN: 0022-1899; 1537-6613
• DOI: 10.1093/infdis/jis589

Background. We conducted a clinical trial in October 2009 to evaluate the immunogenicity of the AS03-adjuvanted influenza vaccine (pH1N1 vaccine) in health care workers (HCWs). By 2 weeks after vaccination, 97% had protective hemagglutinin inhibition (HI) titers (≥40) however, 16% were low responders (LR) and failed to maintain a protective response 90 days after vaccination. Methods. We analyzed the humoral responses (HI, antibody-secreting cell [ASC], and serum immunoglobulin G [IgG]) in 15 LRs and 25 control HCWs. Twelve LRs were revaccinated with the pH1N1 vaccine, and 7 were subsequently vaccinated with the 2010 seasonal trivalent influenza vaccine. We conducted a long-term analysis of the humoral and CD4⁺ T-helper (Th) 1 responses. Results. The LRs had a slower HI antibody response than the control HCWs, with protective antibody titers not reached until 2 weeks after vaccination in the majority of the participants. The LRs also had significantly lower IgG ASCs at day 7 and HA1-specific serum IgG responses at day 21, compared with the control HCWs. Revaccination with the pHlNl vaccine elicited rapid HI antibody, ASC, memory cell, and multifunctional CD4⁺ Thl cell responses. Conclusion. This study shows that revaccination of low-responding HCWs with the pH1N1 vaccine is required for maintaining long-term protection.