A lower than expected adult Victorian community attack rate for pandemic (H1N1) 2009

作者：Grills Nathan; Piers Leonard S; Barr Ian; Vaughan Loretta M; Lester Rosemary; Magliano Dianna J; Shaw Jonathan E; Carnie John A^*

来源：Australian and New Zealand Journal of Public Health, 2010, 34(3): 228-231.

DOI：10.1111/j.1753-6405.2010.00518.x

• Pandemic (H1N1)
• seropositivity
• community attack rate

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.

• 出版日期2010-6