TY - JOUR
T1 - 2009 Influenza A(H1N1) seroconversion rates and risk factors among distinct adult cohorts in Singapore
AU - Chen, Mark I.C.
AU - Lee, Vernon J.M.
AU - Lim, Wei Yen
AU - Barr, Ian G.
AU - Lin, Raymond T.P.
AU - Koh, Gerald C.H.
AU - Yap, Jonathan
AU - Lin, Cui
AU - Cook, Alex R.
AU - Laurie, Karen
AU - Tan, Linda W.L.
AU - Tan, Boon Huan
AU - Loh, Jimmy
AU - Shaw, Robert
AU - Durrant, Chris
AU - Chow, Vincent T.K.
AU - Kelso, Anne
AU - Chia, Kee Seng
AU - Leo, Yee Sin
PY - 2010/4/14
Y1 - 2010/4/14
N2 - Context: Singapore experienced a single epidemic wave of 2009 influenza A(H1N1) with epidemic activity starting in late June 2009 and peaking in early August before subsiding within a month. Objective: To compare the risk and factors associated with H1N1 seroconversion in different adult cohorts. Design, Setting, and Participants: A study with serial serological samples from 4 distinct cohorts: general population (n=838), military personnel (n=1213), staff from an acute care hospital (n=558), and staff as well as residents from long-term care facilities (n=300) from June 22, 2009, to October 15, 2009. Hemagglutination inhibition results of serum samples taken before, during, and after the epidemic and data from symptom questionnaires are presented. Main Outcome Measures: A 4-fold or greater increase in titer between any of the 3 serological samples was defined as evidence of H1N1 seroconversion. Results: Baseline titers of 40 or more were observed in 22 members (2.6%; 95% confidence interval [CI], 1.7%-3.9%) of the community, 114 military personnel (9.4%; 95% CI, 7.9%-11.2%), 37 hospital staff (6.6%; 95% CI, 4.8%-9.0%), and 20 participants from long-term care facilities (6.7%; 95% CI, 4.4%-10.1%). In participants with 1 or more follow-up serum samples, 312 military personnel (29.4%; 95% CI, 26.8%-32.2%) seroconverted compared with 98 community members (13.5%; 95% CI, 11.2%-16.2%), 35 hospital staff (6.5%; 95% CI, 4.7%-8.9%), and only 3 longterm care participants (1.2%; 95% CI, 0.4%-3.5%). Increased frequency of seroconversion was observed for community participants from households in which 1 other member seroconverted (adjusted odds ratio [OR], 3.32; 95% CI, 1.50-7.33), whereas older age was associated with reduced odds of seroconversion (adjusted OR, 0.77 per 10 years; 95% CI, 0.64-0.93). Higher baseline titers were associated with decreased frequency of seroconversion in community (adjusted OR for every doubling of baseline titer, 0.48; 95% CI, 0.27-0.85), military (adjusted OR, 0.71; 95% CI, 0.61-0.81), and hospital staff cohorts (adjusted OR, 0.50; 95% CI, 0.26-0.93). Conclusion: Following the June-September 2009 wave of 2009 influenza A(H1N1), 13% of the community participants seroconverted, and most of the adult population likely remained susceptible.
AB - Context: Singapore experienced a single epidemic wave of 2009 influenza A(H1N1) with epidemic activity starting in late June 2009 and peaking in early August before subsiding within a month. Objective: To compare the risk and factors associated with H1N1 seroconversion in different adult cohorts. Design, Setting, and Participants: A study with serial serological samples from 4 distinct cohorts: general population (n=838), military personnel (n=1213), staff from an acute care hospital (n=558), and staff as well as residents from long-term care facilities (n=300) from June 22, 2009, to October 15, 2009. Hemagglutination inhibition results of serum samples taken before, during, and after the epidemic and data from symptom questionnaires are presented. Main Outcome Measures: A 4-fold or greater increase in titer between any of the 3 serological samples was defined as evidence of H1N1 seroconversion. Results: Baseline titers of 40 or more were observed in 22 members (2.6%; 95% confidence interval [CI], 1.7%-3.9%) of the community, 114 military personnel (9.4%; 95% CI, 7.9%-11.2%), 37 hospital staff (6.6%; 95% CI, 4.8%-9.0%), and 20 participants from long-term care facilities (6.7%; 95% CI, 4.4%-10.1%). In participants with 1 or more follow-up serum samples, 312 military personnel (29.4%; 95% CI, 26.8%-32.2%) seroconverted compared with 98 community members (13.5%; 95% CI, 11.2%-16.2%), 35 hospital staff (6.5%; 95% CI, 4.7%-8.9%), and only 3 longterm care participants (1.2%; 95% CI, 0.4%-3.5%). Increased frequency of seroconversion was observed for community participants from households in which 1 other member seroconverted (adjusted odds ratio [OR], 3.32; 95% CI, 1.50-7.33), whereas older age was associated with reduced odds of seroconversion (adjusted OR, 0.77 per 10 years; 95% CI, 0.64-0.93). Higher baseline titers were associated with decreased frequency of seroconversion in community (adjusted OR for every doubling of baseline titer, 0.48; 95% CI, 0.27-0.85), military (adjusted OR, 0.71; 95% CI, 0.61-0.81), and hospital staff cohorts (adjusted OR, 0.50; 95% CI, 0.26-0.93). Conclusion: Following the June-September 2009 wave of 2009 influenza A(H1N1), 13% of the community participants seroconverted, and most of the adult population likely remained susceptible.
UR - http://www.scopus.com/inward/record.url?scp=77950904361&partnerID=8YFLogxK
U2 - 10.1001/jama.2010.404
DO - 10.1001/jama.2010.404
M3 - Article
SN - 0098-7484
VL - 303
SP - 1383
EP - 1391
JO - JAMA - Journal of the American Medical Association
JF - JAMA - Journal of the American Medical Association
IS - 14
ER -