Open AccessA lower than expected adult Victorian community attack rate for pandemic (H1N1) 2009
Author(s) -
Grills Nathan,
Piers Leonard S.,
Barr Ian,
Vaughan Loretta M.,
Lester Rosemary,
Magliano Dianna J.,
Shaw Jonathan E.,
Carnie John A.
Publication year - 2010
Publication title -
australian and new zealand journal of public health
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.946
H-Index - 76
eISSN - 1753-6405
pISSN - 1326-0200
DOI - 10.1111/j.1753-6405.2010.00518.x
Subject(s) - pandemic , covid-19 , h1n1 pandemic , demography , h1n1 influenza , medicine , geography , virology , sociology , disease , infectious disease (medical specialty) , outbreak
Objectives:To determine the community seropositivity of pandemic (H1N1) 2009 influenza in order to estimate immunity and the community attack rate.Methods:Selected clusters of participants (n=706) in the ‘Victorian Health Monitor’ (VHM), from whom blood samples were taken between August and October 2009, were tested opportunistically for antibodies to pandemic (H1N1) 2009 influenza virus. A titre of ≥1:40 was chosen as the cut‐off for recording seropositivity. The proportion (95% CI) of seropositive participants, aged 18 to <65 years of age, were computed for groups of census collection districts (CDs) across metropolitan Melbourne.Results:The observed pandemic (H1N1) 2009 seropositivity rates for all CDs tested in metropolitan Melbourne was 16.0% (95% CI:12.9‐19.1%); in northern Melbourne subset was 14.4% (95% CI:12.4‐16.3%); and in eastern subset was 16.2% (95% CI:9.7‐22.6%). The pre‐pandemic (H1N1) 2009 positivity rate was estimated at 6%.Conclusion:Given this study's estimate of 16.0% seropositivity in adults in metropolitan Melbourne, and given the WHO laboratory's estimate of 6% pre‐pandemic positivity, the estimated adult community attack rate was 10% for metropolitan Melbourne.Implications:This community attack rate is lower than anticipated and suggests that levels of immunity to Pandemic (H1N1) 2009 might be lower than anticipated. Although limited by a low response rate of 34%, this study suggests low adult seropositivity, which may be useful for public health professionals when encouraging the community to get vaccinated.