(See the Editorial Commentary by Holmberg, on pages 782–3 .) Background. A large outbreak of hepatitis A affected individuals in several Australian states in 2009, resulting in a 2-fold increase in cases reported to state health departments compared with 2008. Two peaks of infection occurred (April–May and September–November), with surveillance data suggesting locally acquired infections from a widely distributed food product. Methods. Two case-control studies were completed. Intensive product trace-back and food sampling was undertaken. Genotyping was conducted on virus isolates from patient serum and food samples. Control measures included prophylaxis for close contacts, public health warnings, an order by the chief health officer under the Victorian Food Act 1984, and trade-level recalls on implicated batches of semidried tomatoes. Results. A multijurisdictional case-control study in April–May found an association between illness and consumption of semidried tomatoes (odds ratio [OR], 3.0; 95% CI 1.4–6.7). A second case-control study conducted in Victoria in October–November also implicated semidried tomatoes as being associated with illness (OR, 10.3; 95% CI, 4.7–22.7). Hepatitis A RNA was detected in 22 samples of semidried tomatoes. Hepatitis A virus genotype IB was identified in 144 of 153 (94%) patients tested from 2009, and partial sequence analysis showed complete identity with an isolate found in a sample of semidried tomatoes. Conclusions. The results of both case-control studies and food testing implicated the novel vehicle of semidried tomatoes as the cause of this hepatitis A outbreak. The outbreak was extensive and sustained despite public health interventions, the design and implementation of which were complicated by limitations in food testing capability and complex supply chains.

Objectives To assess variations by time of year and hospital in the uptake of influenza and pertussis vaccinations by pregnant women in Victoria; to identify factors associated with vaccination uptake. Design, setting Retrospective analysis of data in the Victorian Perinatal Data Collection (VPDC), a population surveillance system for obstetric conditions, procedures, and pregnancy and birth outcomes. Participants Women whose pregnancies ended in a live or stillbirth during July 2015 – June 2017. Main outcome measures Influenza and pertussis vaccinations during pregnancy. Results 153 980 pregnancies in 67 hospitals ended during July 2015 – June 2017; 59 968 pregnant women (39.0%) were vaccinated against influenza and 98 583 (64.0%) against pertussis. Coverage varied by pregnancy end date, rising for influenza during winter and spring, but for pertussis rising continuously across the two years from 37.5% to 82.2%. Differences between hospitals in coverage were marked. Factors associated with vaccination included greater maternal age, primigravidity, early antenatal care, and GP‐led care. The odds of vaccination were statistically significantly lower for women born overseas and those who smoked during pregnancy; the odds of vaccination were also lower for Aboriginal and Torres Strait Islander women. Conclusions Pertussis vaccination of pregnant women in Victoria has increased, but influenza vaccination rates remain moderate and variable. Structural changes at the system level may improve maternal vaccination rates. Embedding the delivery of maternal vaccination programs in antenatal care pathways should be a priority.

BACKGROUND AND OBJECTIVES: Infant influenza and pertussis disease causes considerable morbidity and mortality worldwide. We examined the effectiveness of maternal influenza and pertussis vaccines in preventing these diseases in infants. METHODS: This inception cohort study comprised women whose pregnancies ended between September 1, 2015, and December 31, 2017, in Victoria, Australia. Maternal vaccination status was sourced from the Victorian Perinatal Data Collection and linked to 5 data sets to ascertain infant outcomes and vaccination. The primary outcome of interest was laboratory-confirmed influenza or pertussis disease in infants aged <2 months, 2 to <6 months, and <6 months combined. Secondary outcomes included infant hospitalization (emergency presentation or admission) and death. Risk ratios and 95% confidence intervals (CIs) were estimated by Poisson regression. Vaccine effectiveness (VE) was estimated as (1 minus the risk ratio) x 100%. RESULTS: Among 186 962 pregnant women, 85 830 (45.9%) and 128 060 (68.5%) were vaccinated against influenza and pertussis, respectively. There were 175 and 51 infants with laboratory-confirmed influenza and pertussis disease, respectively. Influenza VE was 56.1% (95% CI, 23.3% to 74.9%) for infants aged <2 months and 35.7% (2.2% to 57.7%) for infants aged 2 to <6 months. Pertussis VE was 80.1% (95% CI, 37.1% to 93.7%) for infants aged <2 months and 31.8% (95% CI, −39.1% to 66.6%) for infants aged 2 to <6 months. CONCLUSIONS: Our study provides evidence of the direct effectiveness of maternal influenza and pertussis vaccination in preventing these diseases in infants aged <2 months. The findings strengthen the importance of maternal vaccination to prevent these diseases in infants.

Interest in the use of emergency department (ED) data by syndromic surveillance systems to detect influenza outbreaks has been growing. Evaluations of these systems generally focus on events during influenza seasons. The aims of this study were to identify which emergency department disease codes best correlated with confirmed influenza cases and to determine if these same codes would be useful in the non-influenza season. The 2009 influenza pandemic in Victoria, Australia, provided further opportunity to examine the performance of the syndromic surveillance system during this event.

SUMMARY: Ross River virus (RRV) is a mosquito-borne virus endemic to Australia. The disease, marked by arthritis, myalgia and rash, has a complex epidemiology involving several mosquito species and wildlife reservoirs. Outbreak years coincide with climatic conditions conducive to mosquito population growth. We developed regression models for human RRV notifications in the Mildura Local Government Area, Victoria, Australia with the objective of increasing understanding of the relationships in this complex system, providing trigger points for intervention and developing a forecast model. Surveillance, climatic, environmental and entomological data for the period July 2000–June 2011 were used for model training then forecasts were validated for July 2011–June 2015. Rainfall and vapour pressure were the key factors for forecasting RRV notifications. Validation of models showed they predicted RRV counts with an accuracy of 81%. Two major RRV mosquito vectors (Culex annulirostrisandAedes camptorhynchus) were important in the final estimation model at proximal lags. The findings of this analysis advance understanding of the drivers of RRV in temperate climatic zones and the models will inform public health agencies of periods of increased risk.