Publications (2)6.9 Total impact
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Article: Incidence of pandemic (H1N1) 2009 influenza infection in children and pregnant women during the 2009 influenza season in Western Australia - a seroprevalence study.
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ABSTRACT: To determine antibody levels and estimate incidence of infection with pandemic (H1N1) 2009 influenza in children and pregnant women during the 2009 winter in Western Australia. Two cross-sectional serosurveys using stored specimens collected for unrelated pathology testing, from before and after (3 August to 30 November 2009) circulation of the pandemic virus, and before commencement of the pandemic vaccination program. Specimens were from three groups: children aged 1-4 years, older children and teenagers aged 5-19 years, and pregnant women aged 21-45 years. The groups were geographically representative of the WA population. Reactivity against pandemic (H1N1) 2009 and seasonal A(H1N1) influenza viruses measured using haemagglutination inhibition (HI) assays. Antibody titres were determined for 648 individuals in the prepandemic period and 736 in the postpandemic period. In the prepandemic period, HI titres ≥ 40 against the pandemic virus were found in 0 (95% CI, 0.0%-1.6%) children aged 1-4 years, 8.3% (95% CI, 5.3%-12.7%) of older children and teenagers, and 4.5% (95% CI, 2.4%-8.3%) of pregnant women. In postpandemic specimens collected from 1 September 2009 (when influenza activity had declined to near-baseline levels), estimated infection rates (subtracting prepandemic levels) were 25.4% (95% CI for difference, 18.6%-33.4%) in 1-4-year-old children, 39.4% (95% CI, 29.8%-48.5%) in older children and teenagers, and 10.2% (95% CI, 4.1%-17.1%) in pregnant women. A quarter of preschool children and about 40% of school-aged children and older teenagers had serological evidence of pandemic influenza infection during winter 2009, indicating high levels of mild or asymptomatic infection. The infection rate in pregnant women was much lower. The high infection rates in children help explain the reduced impact of the pandemic virus during the 2010 winter. Augmented by vaccination, there should be sufficiently high levels of immunity in the Australian population to significantly reduce the impact of the virus in future influenza seasons.The Medical journal of Australia 01/2011; 194(2):68-72. · 2.81 Impact Factor -
Article: The age-specific cumulative incidence of infection with pandemic influenza H1N1 2009 was similar in various countries prior to vaccination.
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ABSTRACT: During the influenza pandemic of 2009 estimates of symptomatic and asymptomatic infection were needed to guide vaccination policies and inform other control measures. Serological studies are the most reliable way to measure influenza infection independent of symptoms. We reviewed all published serological studies that estimated the cumulative incidence of infection with pandemic influenza H1N1 2009 prior to the initiation of population-based vaccination against the pandemic strain. We searched for studies that estimated the cumulative incidence of pandemic influenza infection in the wider community. We excluded studies that did not include both pre- and post-pandemic serological sampling and studies that included response to vaccination. We identified 47 potentially eligible studies and included 12 of them in the review. Where there had been a significant first wave, the cumulative incidence of pandemic influenza infection was reported in the range 16%-28% in pre-school aged children, 34%-43% in school aged children and 12%-15% in young adults. Only 2%-3% of older adults were infected. The proportion of the entire population infected ranged from 11%-18%. We re-estimated the cumulative incidence to account for the small proportion of infections that may not have been detected by serology, and performed direct age-standardisation to the study population. For those countries where it could be calculated, this suggested a population cumulative incidence in the range 11%-21%. Around the world, the cumulative incidence of infection (which is higher than the cumulative incidence of clinical disease) was below that anticipated prior to the pandemic. Serological studies need to be routine in order to be sufficiently timely to provide support for decisions about vaccination.PLoS ONE 01/2011; 6(8):e21828. · 4.09 Impact Factor
