Long COVID in a highly vaccinated but largely unexposed Australian population following the 2022 SARS-CoV-2 Omicron wave: a cross-sectional survey.

OBJECTIVE: To estimate the prevalence of long COVID among Western Australian adults, a highly vaccinated population whose first major exposure to the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was during the 2022 Omicron wave, and to assess its impact on health service use and return to work or study. STUDY DESIGN: Follow-up survey (completed online or by telephone). SETTING, PARTICIPANTS: Adult Western Australians surveyed 90 days after positive SARS-CoV-2 test results (polymerase chain reaction or rapid antigen testing) during 16 July - 3 August 2022 who had consented to follow-up contact for research purposes. MAIN OUTCOME MEASURES: Proportion of respondents with long COVID (ie, reporting new or ongoing symptoms or health problems, 90 days after positive SARS-CoV-2 test result); proportion with long COVID who sought health care for long COVID-related symptoms two to three months after infection; proportion who reported not fully returning to previous work or study because of long COVID-related symptoms. RESULTS: Of the 70 876 adults with reported SARS-CoV-2 infections, 24 024 consented to contact (33.9%); after exclusions, 22 744 people were invited to complete the survey, of whom 11 697 (51.4%) provided complete responses. Our case definition for long COVID was satisfied by 2130 respondents (18.2%). The risk of long COVID was greater for women (v men: adjusted risk ratio [aRR], 1.5; 95% confidence interval [CI], 1.4-1.6) and for people aged 50-69 years (v 18-29 years: aRR, 1.6; 95% CI, 1.4-1.9) or with pre-existing health conditions (aRR, 1.5; 95% CI, 1.4-1.7), as well as for people who had received two or fewer COVID-19 vaccine doses (v four or more: aRR, 1.4; 95% CI, 1.2-1.8) or three doses (aRR, 1.3; 95% CI, 1.1-1.5). The symptoms most frequently reported by people with long COVID were fatigue (1504, 70.6%) and concentration difficulties (1267, 59.5%). In the month preceding the survey, 814 people had consulted general practitioners (38.2%) and 34 reported being hospitalised (1.6%) with long COVID. Of 1779 respondents with long COVID who had worked or studied before the infection, 318 reported reducing or discontinuing this activity (17.8%). CONCLUSION: Ninety days after infection with the Omicron SARS-CoV-2 variant, 18.2% of survey respondents reported symptoms consistent with long COVID, of whom 38.7% (7.1% of all survey respondents) sought health care for related health concerns two to three months after the acute infection.

SARS-CoV-2 Vaccine Effectiveness against Omicron Variant in Infection-Naive Population, Australia, 2022.

SARS-CoV-2 transmission in Western Australia, Australia, was negligible until a wave of Omicron variant infections emerged in February 2022, when >90% of adults had been vaccinated. This unique pandemic enabled assessment of SARS-CoV-2 vaccine effectiveness (VE) without potential interference from background immunity from prior infection. We matched 188,950 persons who had a positive PCR test result during February-May 2022 to negative controls by age, week of test, and other possible confounders. Overall, 3-dose VE was 42.0% against infection and 81.7% against hospitalization or death. A primary series of 2 viral-vectored vaccines followed by an mRNA booster provided significantly longer protection against infection >60 days after vaccination than a 3-dose series of mRNA vaccine. In a population free from non-vaccine-derived background immunity, vaccines against the ancestral spike protein were ≈80% effective for preventing serious outcomes from infection with the SARS-CoV-2 Omicron variant.

Influenza Vaccine Effectiveness in Preventing Influenza-associated Hospitalizations During Pregnancy: A Multi-country Retrospective Test Negative Design Study, 2010-2016.

BACKGROUND: To date, no study has examined influenza vaccine effectiveness (IVE) against laboratory-confirmed influenza-associated hospitalizations during pregnancy. METHODS: The Pregnancy Influenza Vaccine Effectiveness Network (PREVENT) consisted of public health or healthcare systems with integrated laboratory, medical, and vaccination records in Australia, Canada (Alberta and Ontario), Israel, and the United States (California, Oregon, and Washington). Sites identified pregnant women aged 18 through 50 years whose pregnancies overlapped with local influenza seasons from 2010 through 2016. Administrative data were used to identify hospitalizations with acute respiratory or febrile illness (ARFI) and clinician-ordered real-time reverse transcription polymerase chain reaction (rRT-PCR) testing for influenza viruses. Overall IVE was estimated using the test-negative design and adjusting for site, season, season timing, and high-risk medical conditions. RESULTS: Among 19450 hospitalizations with an ARFI discharge diagnosis (across 25 site-specific study seasons), only 1030 (6%) of the pregnant women were tested for influenza viruses by rRT-PCR. Approximately half of these women had pneumonia or influenza discharge diagnoses (54%). Influenza A or B virus infections were detected in 598/1030 (58%) of the ARFI hospitalizations with influenza testing. Across sites and seasons, 13% of rRT-PCR-confirmed influenza-positive pregnant women were vaccinated compared with 22% of influenza-negative pregnant women; the adjusted overall IVE was 40% (95% confidence interval = 12%-59%) against influenza-associated hospitalization during pregnancy. CONCLUSION: Between 2010 and 2016, influenza vaccines offered moderate protection against laboratory-confirmed influenza-associated hospitalizations during pregnancy, which may further inform the benefits of maternal influenza vaccination programs.

Divergent Human-Origin Influenza Viruses Detected in Australian Swine Populations.

Global swine populations infected with influenza A viruses pose a persistent pandemic risk. With the exception of a few countries, our understanding of the genetic diversity of swine influenza viruses is limited, hampering control measures and pandemic risk assessment. Here we report the genomic characteristics and evolutionary history of influenza A viruses isolated in Australia from 2012 to 2016 from two geographically isolated swine populations in the states of Queensland and Western Australia. Phylogenetic analysis with an expansive human and swine influenza virus data set comprising >40,000 sequences sampled globally revealed evidence of the pervasive introduction and long-term establishment of gene segments derived from several human influenza viruses of past seasons, including the H1N1/1977, H1N1/1995, H3N2/1968, and H3N2/2003, and the H1N1 2009 pandemic (H1N1pdm09) influenza A viruses, and a genotype that contained gene segments derived from the past three pandemics (1968, reemerged 1977, and 2009). Of the six human-derived gene lineages, only one, comprising two viruses isolated in Queensland during 2012, was closely related to swine viruses detected from other regions, indicating a previously undetected circulation of Australian swine lineages for approximately 3 to 44 years. Although the date of introduction of these lineages into Australian swine populations could not be accurately ascertained, we found evidence of sustained transmission of two lineages in swine from 2012 to 2016. The continued detection of human-origin influenza virus lineages in swine over several decades with little or unpredictable antigenic drift indicates that isolated swine populations can act as antigenic archives of human influenza viruses, raising the risk of reemergence in humans when sufficient susceptible populations arise.IMPORTANCE We describe the evolutionary origins and antigenic properties of influenza A viruses isolated from two separate Australian swine populations from 2012 to 2016, showing that these viruses are distinct from each other and from those isolated from swine globally. Whole-genome sequencing of virus isolates revealed a high genotypic diversity that had been generated exclusively through the introduction and establishment of human influenza viruses that circulated in past seasons. We detected six reassortants with gene segments derived from human H1N1/H1N1pdm09 and various human H3N2 viruses that circulated during various periods since 1968. We also found that these swine viruses were not related to swine viruses collected elsewhere, indicating independent circulation. The detection of unique lineages and genotypes in Australia suggests that isolated swine populations that are sufficiently large can sustain influenza virus for extensive periods; we show direct evidence of a sustained transmission for at least 4 years between 2012 and 2016.

Antenatal influenza and pertussis vaccination in Western Australia: a cross-sectional survey of vaccine uptake and influencing factors.

BACKGROUND: Influenza and pertussis vaccines have been recommended in Australia for women during each pregnancy since 2010 and 2015, respectively. Estimating vaccination coverage and identifying factors affecting uptake are important for improving antenatal immunisation services. METHODS: A random sample of 800 Western Australian women ≥18 years of age who gave birth between 4th April and 4th October 2015 were selected. Of the 454 (57%) who were contactable by telephone, 424 (93%) completed a survey. Data were weighted by maternal age and area of residence to ensure representativeness. The proportion immunised against influenza and pertussis was the main outcome measure; multivariate logistic regression was used to identify factors significantly associated with antenatal vaccination. Results from the 2015 study were compared to similar surveys conducted in 2012-2014. RESULTS: In 2015, 71% (95% CI 66-75) of women received pertussis-containing vaccine and 61% (95% CI 56-66) received influenza vaccine during pregnancy; antenatal influenza vaccine coverage was 18% higher than in 2014 (43%; 95% CI: 34-46). Pertussis and influenza vaccine were co-administered for 68% of the women who received both vaccines. The majority of influenza vaccinations in 2015 were administered during the third trimester of pregnancy, instead of the second trimester, as was observed in prior years. Women whose care provider recommended both antenatal vaccinations had significantly higher odds of being vaccinated against both influenza and pertussis (OR 33.3, 95% CI: 15.15-73.38). Of unvaccinated mothers, 53.6% (95% CI: 45.9-61.3) and 78.3% (95% CI: 70.4-85.3) reported that they would have been vaccinated against influenza and pertussis, respectively, if their antenatal care provider had recommended it. CONCLUSIONS: Pertussis vaccination coverage was high in the first year of an antenatal immunisation program in Western Australia. Despite a substantial increase in influenza vaccination uptake between 2014 and 2015, coverage remained below that for pertussis. Our data suggest influenza and pertussis vaccination rates of 83% and 94%, respectively, are achievable if providers were to recommend them to all pregnant women.

Antenatal influenza and pertussis vaccine uptake among Aboriginal mothers in Western Australia.

BACKGROUND: Antenatal influenza and pertussis vaccination prevent serious disease in mothers and infants. Aboriginal individuals are at increased risk of infection yet little is known about vaccine coverage among Aboriginal mothers. AIMS: To estimate the uptake of influenza and pertussis vaccination among pregnant Aboriginal women in Western Australia and identify barriers and enablers to vaccination. MATERIALS AND METHODS: Four hundred Aboriginal women, aged ≥18 years, who gave birth to a live infant between April and October 2015, were randomly selected and invited to participate in telephone interviews. Of the 387 women who did not decline, 178 had a functioning phone number and 100 completed the survey. Analyses were weighted by maternal residence. RESULTS: During pregnancy the majority of Aboriginal mothers were recommended influenza (66%; unweighted, 65/96 = 68%) and pertussis (65%; unweighted, 62/94 = 66%) vaccines, with 62% (unweighted, 56/94 = 56%) and 63% (unweighted, 60/93 = 65%) receiving the vaccinations, respectively. Almost all vaccinated women (98%) reported wanting to protect their baby as the reason for immunisation. Rural mothers were more likely than metropolitan mothers to have been vaccinated against influenza (odds ratio (OR) 4.1, 95% CI 1.7-10.2) and pertussis (OR 3.1, 95% CI 1.2-7.6). Recommendation by a healthcare provider was strongly associated with vaccine uptake (influenza: OR 15.6, 95% CI 4.9-49.5; pertussis: OR 13.3, 95% CI 4.6-38.0). CONCLUSION: Vaccination uptake among Western Australian Aboriginal mothers is comparable with rates reported for non-Aboriginal populations worldwide. Provider recommendation is the single most important factor associated with vaccination uptake, underlining the importance of integrating vaccination into routine antenatal care.

Randomized Controlled Trial of Text Message Reminders for Increasing Influenza Vaccination.

PURPOSE: Seasonal influenza vaccine is recommended and funded for groups at higher risk of serious infection, but uptake is suboptimal. We conducted a randomized controlled trial of short message service (SMS) reminders for influenza vaccination. METHODS: Six weeks after seasonal influenza vaccinations began, we identified high-risk patients who had a mobile telephone number on record at 10 practices in Western Australia. Thirty-two percent of the selected patients had already been vaccinated in the current year and were ineligible. Of the remaining 12,354 eligible patients at each practice one-half were randomly assigned to receive a vaccination reminder by SMS (intervention) and the rest received no SMS (control). Approximately 3 months after the SMS was sent (the study period), vaccination data were extracted from the patients' electronic medical records. Log-binomial regression models were used to calculate the relative risk (RR) of vaccination between the intervention and control group. RESULTS: Twelve-percent (769 of 6,177) of the intervention group and 9% (548 of 6,177) of the control group were vaccinated during the study period, a 39% relative increase attributable to the SMS (RR = 1.39; 95% CI, 1.26-1.54). For every 29 SMSs sent, costing $3.48, 1 additional high-risk patient was immunized. The greatest effect was observed for children younger than 5 years, whose parents were more than twice as likely to have their child vaccinated if they received a SMS reminder (RR = 2.43; 95% CI, 1.79-3.29). CONCLUSION: We found SMS reminders to be a modestly effective, low-cost means to increase seasonal influenza vaccine coverage among high-risk patients.

Seasonal Trivalent Influenza Vaccination During Pregnancy and the Incidence of Stillbirth: Population-Based Retrospective Cohort Study.

BACKGROUND: Although antenatal influenza vaccination is an important public health intervention for preventing serious infection in pregnant women and newborns, reported vaccine coverage is often <50%. Concern for the safety to the fetus is a commonly cited reason for vaccine hesitancy and refusal. The incidence of stillbirth following pandemic vaccination has been previously studied; however, no population-based study has evaluated the incidence of stillbirth following seasonal trivalent influenza vaccination. METHODS: We used probabilistic linking of perinatal and maternal vaccination records to establish a cohort of 58 008 births occurring between April 2012 and December 2013. Stillbirth was defined as birth ≥20 weeks' gestation with an Apgar score of zero at 1 and 5 minutes following delivery. Cox regression models adjusted for maternal smoking, Indigenous status, and propensity for vaccination were used to calculate adjusted hazard ratios (aHRs) in vaccinated and unvaccinated mothers. RESULTS: A total of 5076 (8.8%) pregnant women received trivalent influenza vaccine and 377 stillbirths occurred. There were 5.0 and 3.0 stillbirths per 100 000 pregnancy-days among unvaccinated and vaccinated women, respectively. After adjustment, stillbirth was 51% less likely among vaccinated vs unvaccinated mothers (aHR, 0.49; 95% confidence interval [CI], .29-.84). The largest relative reduction in stillbirths was observed for births occurring just after influenza season (aHR, 0.33; 95% CI, .12-.88). CONCLUSIONS: Mothers who received seasonal TIV during pregnancy were significantly less likely to experience stillbirth compared with unvaccinated mothers. These results support the safety of seasonal influenza immunization during pregnancy and suggest a protective effect.

An observational study of febrile seizures: the importance of viral infection and immunization.

BACKGROUND: Febrile seizures are common in young children. Annual peaks in incidence mirror increased respiratory virus activity during winter. Limited virological data are available using modern diagnostic techniques for children with febrile seizures. We aimed to determine the frequency of detection of specific viral pathogens in children with febrile seizures, to describe risk factors including recent vaccination and clinical features associated with specific etiologies. METHODS: An observational study was performed. Children aged 6 months to 5 years presenting to the Emergency Department of a tertiary children's hospital in Western Australia with febrile seizures were enrolled between March 2012 and October 2013. Demographic, clinical data and vaccination history were collected, and virological testing was performed on per-nasal and per-rectal samples. RESULTS: One hundred fifty one patients (72 female; median age 1.7y; range 6 m-4y9m) were enrolled. Virological testing was completed for 143/151 (95%). At least one virus was detected in 102/143 patients (71%). The most commonly identified were rhinoviruses (31/143, 22%), adenovirus (30/151, 21%), enteroviruses, (28/143, 20%), influenza (19/143, 13%) and HHV6 (17/143, 12%). More than one virus was found in 48/143 (34%). No significant clinical differences were observed when children with a pathogen identified were compared with those with no pathogen detected. Febrile seizures occurred within 14 days of vaccine administration in 16/151 (11%). CONCLUSION: At least one virus was detected in over two thirds of cases tested (commonly picornaviruses, adenovirus and influenza). Viral co-infections were frequently identified. Febrile seizures occurred infrequently following immunization.

A prospective cohort study comparing the reactogenicity of trivalent influenza vaccine in pregnant and non-pregnant women.

BACKGROUND: Influenza vaccination during pregnancy can prevent serious illness in expectant mothers and provide protection to newborns; however, historically uptake has been limited due to a number of factors, including safety concerns. Symptomatic complaints are common during pregnancy and may be mistakenly associated with reactions to trivalent influenza vaccine (TIV). To investigate this, we compared post-vaccination events self-reported by pregnant women to events reported by non-pregnant women receiving TIV. METHODS: A prospective cohort of 1,086 pregnant women and 314 non-pregnant female healthcare workers (HCWs) who received TIV between March-May 2014 were followed-up seven days post-vaccination to assess local and systemic adverse events following immunisation (AEFIs). Women were surveyed by text message regarding perceived reactions to TIV. Those reporting an AEFI completed an interview by telephone or mobile phone to ascertain details. Logistic regression models adjusting for age and residence were used to compare reactions reported by pregnant women and non-pregnant HCWs. RESULTS: Similar proportions of pregnant women and non-pregnant, female HCWs reported ≥1 reaction following vaccination with TIV (13.0% and 17.3%, respectively; OR = 1.2 [95% CI: 0.8-1.8]). Non-pregnant, female HCWs were more likely to report fever or headache compared to pregnant women (OR: 4.6 [95% CI 2.1-10.3] and OR: 2.2 [95% CI 1.0-4.6], respectively). No other significant differences in reported symptoms were observed. No serious vaccine-associated adverse events were reported, and less than 2% of each group sought medical advice for a reaction. CONCLUSIONS: We found no evidence suggesting pregnant women are more likely to report adverse events following influenza vaccination when compared to non-pregnant female HCWs of similar age, and in some cases, pregnant women reported significantly fewer adverse events. These results further support the safety of TIV administered in pregnant women.

Surveillance of antenatal influenza vaccination: validity of current systems and recommendations for improvement.

BACKGROUND: Although influenza vaccination is recommended during pregnancy as standard of care, limited surveillance data are available for monitoring uptake. Our aim was to evaluate the validity of existing surveillance in Western Australia for measuring antenatal influenza immunisations. METHODS: The self-reported vaccination status of 563 women who delivered between April and October 2013 was compared against three passive data collection sources: a state-wide antenatal influenza vaccination database maintained by the Department of Health, a public maternity hospital database, and a private health service database. Sensitivity, specificity, and positive and negative predictive values were calculated for each system using self-report as the "gold standard." RESULTS: The state-wide antenatal vaccination database detected 45.7 % (95 % CI: 40.1-51.4 %) of influenza vaccinations, the public maternity hospital database detected 66.7 % (95 % CI: 55.1-76.9 %), and the private health service database detected 29.1 % (95 % CI: 20.5-39.4 %). Specificity exceeded 90 % and positive predictive values exceeded 80 % for each system. Sensitivity was lowest for women whose antenatal care was provided by a private obstetrician. CONCLUSIONS: Existing resources for surveillance of antenatal influenza vaccinations detect 29-67 % of vaccinations. Considering the importance of influenza immunisation as a public health intervention, particularly in pregnant women, improvements to routine monitoring of influenza vaccination is warranted.

Antenatal care provider's advice is the key determinant of influenza vaccination uptake in pregnant women.

BACKGROUND: Although influenza vaccination is an important component of antenatal care and is recommended and funded by the Australian government, vaccination uptake has been low. AIMS: This study compared seasonal influenza vaccination uptake among pregnant Western Australian (WA) women and identified factors associated with vaccination uptake. MATERIALS AND METHODS: Adult women who were pregnant during the 2012 and 2013 influenza vaccination seasons were selected at random and invited to complete a computer-assisted telephone interview survey about whether they received influenza vaccination during pregnancy. Data analyses were weighted to the age distribution of women of reproductive age in WA. Multivariate logistic regression was used to identify factors associated with vaccination uptake. RESULTS: Between 2012 and 2013, the proportion of WA women whose antenatal care provider recommended influenza vaccination increased from 37.6 to 62.1% and vaccination uptake increased from 23.0 to 36.5%. The antenatal care provider's advice to have influenza vaccine was the single most important factor associated with vaccination (OR 11.1, 95% CI 7.9-15.5). Most women (63.7%) were vaccinated in general practice, 18.8% in a public hospital antenatal clinic and 11.0% at their workplace. Wanting to protect their infant from infection (91.2%) and having the vaccine recommended by their GP (60.0%) or obstetrician (51.0%) were commonly reported reasons for vaccination; worrying about side effects was a common reason for nonvaccination. CONCLUSIONS: To optimise maternal and infant health outcomes, Australian antenatal care providers and services need to incorporate both the recommendation and delivery of influenza vaccination into routine antenatal care.

Using automated text messages to monitor adverse events following immunisation in general practice.

OBJECTIVE: To assess the performance of SmartVax, a prototypic active monitoring system for adverse events following immunisation (AEFI) using short message service (SMS) text messages and clinical data extracted from commercially available medical practice management software. DESIGN, SETTING AND PARTICIPANTS: Between 11 November 2011 and 10 June 2013, adult patients and parents of paediatric patients receiving routine vaccinations in general practice were sent an SMS by SmartVax enquiring if they had experienced any AEFI and requesting a reply by SMS. Attempts were made to telephone patients who did not reply by SMS. MAIN OUTCOME MEASURES: The proportion of patients sent an SMS who replied by SMS, and the proportion of respondents indicating possible AEFI. RESULTS: Of 3281 vaccinated patients, 3226 (98.3%) had a mobile telephone number on record and were sent an SMS. Of 2342 patients (72.6%; 95% CI, 70.0%-75.1%) who responded by SMS, 264 (11.3%; 95 CI, 9.9%-12.7%) reported possible AEFI. The response rate was ≥ 70% for both paediatric and adult patients. Eighty-per cent of SMS replies were received within 2 hours of transmission of the query SMS. There was no significant difference in the proportion reporting possible AEFI between patients who replied by SMS and those who did not respond by SMS but were subsequently contacted by a telephone call (P = 0.99). CONCLUSIONS: More than 70% of patients responded by SMS to an SMS query about whether they had any vaccine reactions, with the data received in near real-time. Active surveillance of AEFI using SMS has the capacity to complement existing passive reporting systems, potentially permitting more rapid identification of emerging safety signals.

Using SMS to monitor adverse events following trivalent influenza vaccination in pregnant women.

BACKGROUND: Trivalent influenza vaccine (TIV) has been recommended for pregnant women in Australia for more than a decade and funded since 2009, yet vaccination coverage remains low. Misperceptions of the safety of TIV in pregnancy have been identified as a major contributor to low vaccination rates. Ongoing safety monitoring with dissemination of results could help improve antenatal influenza vaccine uptake. AIM: To implement a real-time safety monitoring program for TIV administered to pregnant women. MATERIALS AND METHODS: Between March and July 2013, a cohort of 3,173 pregnant women who received the 2013 TIV agreed to follow-up regarding possible adverse events following immunisation (AEFI); 3,047 (96%) provided a mobile telephone number and were sent a short message service (SMS) inquiring whether they had experienced an AEFI; attempts were made to contact the remaining 126 (4%) women by voice telephone call. RESULTS: Responses were obtained from 2,885 (90.9%) women, 413 (14.3%) of whom reported a suspected AEFI. Local reactions were the most frequently reported AEFI (4.9%), followed by headache (3.3%), fever (2.7%), fatigue (2.5%), diarrhoea (2.5%) and malaise (1.2%); 39 women (1.4%) sought medical advice and no serious vaccine-related AEFIs were identified. Response rates were higher for SMS compared to telephone (84% vs 63%; P < 0.001). CONCLUSIONS: These findings support the safety of TIV in pregnant women. Mobile phone technology proved an efficient method for timely surveillance of adverse events following vaccination. The low level of AEFI observed should be reassuring to antenatal patients and their providers and help promote TIV uptake.

Predictors of uptake of influenza vaccination--a survey of pregnant women in Western Australia.

BACKGROUND: Pregnant women are at increased risk of complications following influenza infection. Vaccination is the most effective preventive strategy. This survey aimed to determine the levels of uptake of influenza vaccine in pregnant women in Western Australia (WA), the proportion of women offered vaccination as part of antenatal care, and women's attitudes toward influenza vaccination in pregnancy. METHODS: Computer assisted telephone interviews were conducted with 416 randomly selected women who were pregnant during the 2012 influenza vaccination season. RESULTS: Influenza vaccination coverage was 23%. Predictors of vaccination included believing that vaccination is safe for the infant, having been recommended vaccination by an antenatal care provider, and attending a general practitioner for most antenatal care. The majority (74%) of unvaccinated women reported that they would have the vaccine if their antenatal care provider recommended it. DISCUSSION: General practitioners lead the way in antenatal influenza vaccination in WA. Vaccination coverage can be improved if recommending and offering influenza vaccination becomes a routine part of antenatal care.

Influenza vaccination in Western Australian children: Exploring the health benefits and cost savings of increased vaccine coverage in children.

Introduction: To assess potential benefits and direct healthcare cost savings with expansion of an existing childhood influenza immunisation program, we developed a dynamic transmission model for the state of Western Australia, evaluating increasing coverage in children < 5 years and routinely immunising school-aged children. Methods: A deterministic compartmental Susceptible-Exposed-Infectious-Recovered age-stratified transmission model was developed and calibrated using laboratory-notification and hospitalisation data. Base case vaccine coverage estimates were derived from 2019 data and tested under moderate, low and high vaccine effectiveness settings. The impact of increased coverage on the burden of influenza, influenza-associated presentations and net costs were assessed using the transmission model and estimated health utilisation costs. Results: Under base case vaccine coverage and moderate vaccine effectiveness settings, 225,460 influenza cases are expected annually across all ages. Direct healthcare costs of influenza were estimated to be A$27,608,286 per annum, dominated by hospital costs. Net cost savings of >$A1.5 million dollars were observed for every 10 % increase in vaccine coverage in children < 5 years. Additional benefits were observed by including primary school age children (5-11 years) in the funded influenza vaccination program - a reduction in cases, presentations, hospitalisations and approximately $A4 million net costs savings were observed for every 10 % increase in coverage. The further addition of older children (12-17 years) resulted in only moderate additional net cost savings figures, compared with a 5-11year-old program alone. Net costs savings were predominantly derived by a reduction in influenza-associated hospitalisation in adults. Conclusions: Any increase in influenza vaccine coverage in children < 5 years, above a base case of 50 % coverage resulted in a substantive reduction in influenza cases, presentations, hospitalisations and net costs when applied to the West Australian population. However, the most impactful pediatric program, from both a disease prevention and costs perspective, would be one that increased vaccination coverage among primary-school aged children.

Maternal Pertussis Vaccination, Infant Immunization, and Risk of Pertussis.

OBJECTIVES: Following the introduction of jurisdictional maternal pertussis vaccination programs in Australia, we estimated maternal vaccine effectiveness (VE) and whether maternal pertussis vaccination modified the effectiveness of the first 3 primary doses of pertussis-containing vaccines. METHODS: We conducted a population-based cohort study of 279 418 mother-infant pairs using probabilistic linkage of administrative health records in 3 Australian jurisdictions. Infants were maternally vaccinated if their mother had a documented pertussis vaccination ≥14 days before birth. Jurisdictional immunization records were used to identify receipt of the first 3 infant doses of pertussis-containing vaccines. Infant pertussis infections were identified using notifiable disease records. VE was estimated using Cox proportional hazard models. RESULTS: Pertussis was administered during 51.7% (n = 144 429/279 418) of pregnancies, predominantly at 28-31 weeks' gestation. VE of maternal pertussis vaccination declined from 70.4% (95% confidence interval [CI], 50.5-82.3) among infants <2 months old to 43.3% (95% CI, 6.8-65.6) among infants 7-8 months old and was not significant after 8 months of age. Although we observed slightly lower VE point estimates for the third dose of infant pertussis vaccine among maternally vaccinated compared with unvaccinated infants (76.5% vs 92.9%, P = .002), we did not observe higher rates of pertussis infection (hazard ratio, 0.70; 95% CI, 0.61-3.39). CONCLUSIONS: Pertussis vaccination near 28 weeks' gestation was associated with lower risk of infection among infants through 8 months of age. Although there was some evidence of lower effectiveness of infant vaccination among maternally vaccinated infants, this did not appear to translate to greater risk of disease.

Travel-associated SARS-CoV-2 transmission documented with whole genome sequencing following a long-haul international flight.

BACKGROUND: Multiple instances of flight-associated severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission during long-haul flights have been reported during the COVID-19 pandemic. However, comprehensive investigations of passenger risk behaviours, before, during and after the flight, are scarce. METHODS: To investigate suspected SARS-CoV-2 transmission during a flight from United Arab Emirates to Australia in July 2020, systematic, repeated polymerase chain reaction (PCR) testing of passengers in hotel quarantine was linked to whole genome sequencing. Epidemiological analyses of in-depth interviews covering behaviours during the flight and activities pre- and post-boarding were used to identify risk factors for infection. RESULTS: Seventeen of the 95 passengers from four different travel origins had PCR-confirmed infection yielding indistinguishable genomic sequences. Two of the 17 passengers were symptomatic within 2 days of the flight, and classified as co-primary cases. Seven secondary cases were seated within two rows of the co-primary cases, but five economy passengers seated further away and three business class passengers were also infected (attack rate = 16% [15/93]). In multivariable analysis, being seated within two rows of a primary case [odds ratio (OR) 7.16; 95% confidence interval (CI) 1.66-30.85] and spending more than an hour in the arrival airport (OR 4.96; 95% CI 1.04-23.60) were independent predictors of secondary infection, suggesting travel-associated SARS-CoV-2 transmission likely occurred both during and after the flight. Self-reported increased hand hygiene, frequent aisle walking and using the bathroom on the plane did not independently affect the risk of SARS-CoV-2 acquisition. CONCLUSIONS: This investigation identified substantial in-flight transmission among passengers seated both within and beyond two rows of the primary cases. Infection of passengers in separate cabin classes also suggests transmission occurred outside the cabin environment, likely at the arrival airport. Recognizing that transmission may occur pre- and post-boarding may inform contact tracing advice and improve efforts to prevent future travel-associated outbreaks.

Leptospirosis in Hawaii, USA, 1999-2008.

Although infrequently diagnosed in the United States, leptospirosis is a notable reemerging infectious disease throughout developing countries. Until 1995, when the disease was eliminated from the US list of nationally notifiable diseases, Hawaii led the nation in reported annual incidence rates. Leptospirosis remains a notifiable disease in Hawaii. To ascertain the status of leptospirosis in Hawaii since the most recent US report in 2002, we reviewed 1999-2008 data obtained from case investigation reports by the Hawaii State Department of Health. Of the 345 case reports related to in-state exposures, 198 (57%) were laboratory confirmed. Our findings indicate a change in seasonal disease occurrence from summer to winter and in the infective serogroup from Icterohemorrhagiae to Australis. Also, during the past 20 years, recreational exposures have plateaued, while occupational exposures have increased. Ongoing surveillance is needed to clarify and track the dynamic epidemiology of this widespread zoonosis.