Long-term immunogenicity of the pandemic influenza A/H1N1 2009 vaccine among health care workers: influence of prior seasonal influenza vaccination.
Health care workers (HCWs) are at great risk of influenza infection and transmission. Vaccination for seasonal influenza is routinely recommended, but this strategy should be reconsidered in a pandemic situation. Between October 2009 and September 2010, a multicenter study was conducted to assess the long-term immunogenicity of the A/H1N1 2009 monovalent influenza vaccine among HCWs compared to non-health care workers (NHCWs). The influence of prior seasonal influenza vaccination was also assessed with respect to the immunogenicity of pandemic H1N1 influenza vaccine. Serum hemagglutinin inhibition titers were determined prevaccination and then at 1, 6, and 10 months after vaccination. Of the 360 enrolled HCW subjects, 289 participated in the study up to 10 months after H1N1 monovalent influenza vaccination, while 60 of 65 NHCW subjects were followed up. Seroprotection rates, seroconversion rates, and geometric mean titer (GMT) ratios fulfilled the European Union's licensure criteria for influenza A/California/7/2009 (H1N1) at 1 month after vaccination in both the HCWs and NHCWs, without any significant difference. At 6 months after vaccination, the seroprotection rate was more significantly lowered among the NHCWs than among the HCWs (P < 0.01). Overall, postvaccination (1, 6, and 10 months after vaccination) GMTs for A/California/7/2009 (H1N1) were significantly lower among the seasonal influenza vaccine recipients than among the nonrecipients (P < 0.05). In conclusion, HCWs should be encouraged to receive an annual influenza vaccination, considering the risk of repeated exposure. However, prior reception of seasonal influenza vaccine showed a negative influence on immunogenicity for the pandemic A/H1N1 2009 influenza vaccine.
Division of Infectious Diseases, Department of Internal Medicine, Korea University College of Medicine, Seoul, South Korea.
Joon Young
JY
Song
Hee Jin
HJ
Cheong
Yu Bin
YB
Seo
In Seon
IS
Kim
Ji Yun
JY
Noh
Won Suk
WS
Choi
Jacob
J
Lee
Hye Won
HW
Jeong
Sae Yoon
SY
Kee
Woo Joo
WJ
Kim
D000328:Adult; D000914:Antibodies, Viral / Q000097:blood; D005260:Female; D005500:Follow-Up Studies; D006282:Health Personnel; D006385:Hemagglutination Inhibition Tests; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology*; D007252:Influenza Vaccines / Q000008:administration & dosage / Q000276:immunology*; D007251:Influenza, Human / Q000517:prevention & control* / Q000821:virology; D008297:Male; D008875:Middle Aged; D013997:Time Factors; D014611:Vaccination / Q000379:methods*; D055815:Young Adult
D000914:Antibodies, Viral; D007252:Influenza Vaccines