Cross-reactive Antibody Response to the Pandemic A (H1N1) 2009 Influenza Virus induced by vaccination with a seasonal trivalent influenza vaccine: A Longitudinal Study of Three Influenza Seasons in Japan.
ABSTRACT The cross-reactivity of antibody to the swine-origin pandemic influenza A (H1N1) 2009 virus induced by vaccination with a seasonal trivalent influenza vaccine was studied. Paired sera from a cohort of adult volunteers vaccinated with a trivalent seasonal influenza vaccine every year from 2006 to 2008 were collected each year and tested by hemagglutination inhibition (HI) for antibody against the pandemic influenza A (H1N1) 2009 virus. There was little increase in the geometric mean titer overall; a slight increase was detected in the sera obtained in the 2007-2008 season but not in the other two seasons. The proportion of individuals with HI antibody titer ≥1:40 did not change significantly from year to year. These results indicated that cross-reactivity of the antibodies induced by a trivalent seasonal vaccine to the pandemic influenza A (H1N1) 2009 virus is marginal.
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ABSTRACT: A 69-year-old man with a history of hepatitis C since May 1985 and his 6 healthy immediate relatives were examined for hemagglutination inhibition antibodies against 2009 pandemic influenza A/H1N1 virus. This patient had a hemagglutination inhibition antibody titer of 640 against 2009 pandemic influenza A/H1N1 virus in a serum sample collected on July 4, 1999, and the antibody titers fluctuated between 40 and 320 in serum samples collected after 1999. The fluctuations in hemagglutination inhibition antibody titers against pandemic 2009 influenza A/H1N1 virus were not consistent with his history of seasonal influenza, and our results suggest a relationship to his vaccination with seasonal trivalent inactivated influenza vaccine. This patient as well as three relatives showed cross-reactive antibody titers of 10 or more against 2009 pandemic A/H1N1 influenza virus in serum samples taken after June 1999. From these results we conclude that the cross-reactivity to pandemic 2009 A/H1N1 influenza virus emerged after June 1999.Human vaccines & immunotherapeutics. 01/2013; 9(5).
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ABSTRACT: Background Healthcare workers in primary care are at risk of infection during an influenza pandemic. The 2009 influenza pandemic provided an opportunity to assess this risk. Aim To measure the prevalence of seropositivity to influenza A(H1N1)pdm09 among primary healthcare workers in Canterbury, New Zealand, following the 2009 influenza pandemic, and to examine associations between seropositivity and participants' sociodemographic characteristics, professional roles, work patterns, and seasonal influenza vaccination status. Design and setting An observational study involving a questionnaire and testing for influenza A(H1N1)pdm09 seropositivity in all primary healthcare workers in Canterbury, New Zealand between December 2009 and February 2010. Method Participants completed a questionnaire that recorded sociodemographic and professional data, symptoms of influenza-like illness, history of seasonal influenza vaccination, and work patterns. Serum samples were collected and haemagglutination inhibition antibody titres to influenza A(H1N1)pdm09 measured. Results Questionnaires and serum samples were received from 1027 participants, from a workforce of 1476 (response rate 70%). Seropositivity was detected in 224 participants (22%). Receipt of seasonal influenza vaccine (odds ratio [OR] = 2.0, 95% confidence interval [CI] = 1.2 to 3.3), recall of influenza (OR = 1.9, 95% CI = 1.3 to 2.8), and age ≤45 years (OR = 1.4, 95% CI = 1.0 to 1.9) were associated with seropositivity. Conclusion A total of 22% of primary care healthcare workers were seropositive. Younger participants, those who recalled having influenza, and those who had been vaccinated against seasonal influenza were more likely to be seropositive. Working in a dedicated influenza centre was not associated with an increased risk of seropositivity.British Journal of General Practice 06/2013; 63(611):416-22. · 2.03 Impact Factor