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A(H1N1)PDM09 VACCINATION OF HEALTH CARE WORKERS: IMPROVED IMMUNE RESPONSES IN LOW RESPONDERS FOLLOWING REVACCINATION.
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Pathirana RD, Bredholt G, Akselsen PE, Pedersen GK, Cox RJ.
J Infect Dis. 2012 Oct 12. [Epub ahead of print]
http://jid.oxfordjournals.org/content/early/2012/10/11/infdis.jis589.long
Abstract

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) (www.clinicaltrials.gov, NCT01003288). 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 pH1N1 vaccine elicited rapid HI antibody, ASC, memory B cell, and multifunctional CD4(+) Th1 cell responses.
Conclusion. This study shows that revaccination of low-responding HCWs with the pH1N1 vaccine is required for maintaining long-term protection.

PMID: 22969149 [PubMed - as supplied by publisher]