ABSTRACT
During 2010-2012 the strain composition of the influenza vaccine in the Southern Hemisphere did not change, but the circulating virus type/subtype did. We pooled data for these years from the Western Australian sentinel medical practice surveillance system for influenza to estimate vaccine effectiveness (VE) by influenza virus type and subtype. A case test-negative design was used with VE estimated as (1-odds ratio)×100%. There were 2182 patients included in the analysis across the 3 years studied. The predominant subtype was A/H1pdm09 in 2010 and 2011, and A/H3 in 2012. The overall adjusted VE estimate against all influenza for 2010-2012 was 51% (95% CI: 36, 63). Estimates were highest against A/H1pdm09 at 74% (95% CI: 47, 87), followed by 56% (95% CI: 33, 71) for influenza B and lowest against A/H3 at 39% (95% CI: 13, 57). When analyses were restricted to compare influenza-positive patients with patients who tested positive for a non-influenza virus, overall adjusted VE was 59% (95% CI: 39, 72). These results suggest moderate protection against influenza by vaccination in Western Australia over the period 2010-2012, and are consistent with findings from other settings.
Subject(s)
Influenza Vaccines/therapeutic use , Influenza, Human/prevention & control , Sentinel Surveillance , Adolescent , Adult , Aged , Aged, 80 and over , Case-Control Studies , Child , Child, Preschool , Female , Humans , Infant , Infant, Newborn , Influenza A Virus, H1N1 Subtype , Influenza A Virus, H3N2 Subtype , Influenza B virus , Influenza Vaccines/immunology , Influenza, Human/epidemiology , Influenza, Human/virology , Male , Middle Aged , Odds Ratio , Western Australia/epidemiology , Young AdultABSTRACT
A real-time reverse transcription PCR (rRT-PCR) assay was designed and evaluated for the detection of the point mutation in the influenza A N1 neuraminidase gene that results in a tyrosine to histidine substitution at amino acid position 275 (H275Y) causing resistance to oseltamivir, an antiviral neuraminidase inhibitor. The rRT-PCR assays detected the presence or absence of the H275Y mutation in 387/388 (99.7%) of clinical samples containing the pandemic influenza A/H1N1 2009 virus. The H275Y mutation was not detected in any of the community patient samples (0/132) but was detected in four hospitalized patients who had been treated with oseltamivir for several days. The sensitive rRT-PCR assays may be performed directly on patient specimens, can detect resistant virus at low levels, and therefore may provide early warning of developing resistance within individual patients or the wider population.