Effectiveness of COVID-19 vaccines administered in the 2023 autumnal campaigns in Europe: Results from the VEBIS primary care test-negative design study, September 2023-January 2024.

In autumn 2023, European vaccination campaigns predominantly administered XBB.1.5 vaccine. In a European multicentre study, we estimated 2023 COVID-19 vaccine effectiveness (VE) against laboratory-confirmed symptomatic infection at primary care level between September 2023 and January 2024. Using a test-negative case-control design, we estimated VE in the target group for COVID-19 vaccination overall and by time since vaccination. We included 1057 cases and 4397 controls. Vaccine effectiveness was 40 % (95 % CI: 26-53 %) overall, 48 % (95 % CI: 31-61 %) among those vaccinated < 6 weeks of onset and 29 % (95 % CI: 3-49 %) at 6-14 weeks. Our results suggest that COVID-19 vaccines administered to target groups during the autumn 2023 campaigns showed clinically significant effectiveness against laboratory-confirmed, medically attended symptomatic SARS-CoV-2 infection in the 3 months following vaccination. A longer study period will allow for further variant-specific COVID-19 VE estimates, better understanding decline in VE and informing booster administration policies.

Exploring the effect of clinical case definitions on influenza vaccine effectiveness estimation at primary care level: Results from the end-of-season 2022-23 VEBIS multicentre study in Europe.

BACKGROUND: Within influenza vaccine effectiveness (VE) studies at primary care level with a laboratory-confirmed outcome, clinical case definitions for recruitment of patients can vary. We used the 2022-23 VEBIS primary care European multicentre study end-of-season data to evaluate whether the clinical case definition affected IVE estimates. METHODS: We estimated VE using a multicentre test-negative case-control design. We measured VE against any influenza and influenza (sub)types, by age group (0-14, 15-64, ≥65 years) and by influenza vaccine target group, using logistic regression. We estimated IVE among patients meeting the European Union (EU) acute respiratory infection (ARI) case definition and among those meeting the EU influenza-like illness (ILI) case definition, including only sites providing information on specific symptoms and recruiting patients using an ARI case definition (as the EU ILI case definition is a subset of the EU ARI one). RESULTS: We included 24 319 patients meeting the EU ARI case definition, of whom 21 804 patients (90 %) meet the EU ILI case definition, for the overall pooled VE analysis against any influenza. The overall and influenza (sub)type-specific VE varied by ≤2 % between EU ILI and EU ARI populations. DISCUSSION: Among all analyses, we found similar VE estimates between the EU ILI and EU ARI populations, with few (10%) additional non-ILI ARI patients recruited. These results indicate that VE in the 2022-23 influenza season was not affected by use of a different clinical case definition for recruitment, although we recommend investigating whether this holds true for next seasons.

COVID-19 vaccine effectiveness against symptomatic infection with SARS-CoV-2 BA.1/BA.2 lineages among adults and adolescents in a multicentre primary care study, Europe, December 2021 to June 2022.

BackgroundScarce European data in early 2021 suggested lower vaccine effectiveness (VE) against SARS-CoV-2 Omicron lineages than previous variants.AimWe aimed to estimate primary series (PS) and first booster VE against symptomatic BA.1/BA.2 infection and investigate potential biases.MethodsThis European test-negative multicentre study tested primary care patients with acute respiratory symptoms for SARS-CoV-2 in the BA.1/BA.2-dominant period. We estimated PS and booster VE among adults and adolescents (PS only) for all products combined and for Comirnaty alone, by time since vaccination, age and chronic condition. We investigated potential bias due to correlation between COVID-19 and influenza vaccination and explored effect modification and confounding by prior SARS-CoV-2 infection.ResultsAmong adults, PS VE was 37% (95% CI: 24-47%) overall and 60% (95% CI: 44-72%), 43% (95% CI: 26-55%) and 29% (95% CI: 13-43%) < 90, 90-179 and ≥ 180 days post vaccination, respectively. Booster VE was 42% (95% CI: 32-51%) overall and 56% (95% CI: 47-64%), 22% (95% CI: 2-38%) and 3% (95% CI: -78% to 48%), respectively. Primary series VE was similar among adolescents. Restricting analyses to Comirnaty had little impact. Vaccine effectiveness was higher among older adults. There was no signal of bias due to correlation between COVID-19 and influenza vaccination. Confounding by previous infection was low, but sample size precluded definite assessment of effect modification.ConclusionPrimary series and booster VE against symptomatic infection with BA.1/BA.2 ranged from 37% to 42%, with similar waning post vaccination. Comprehensive data on previous SARS-CoV-2 infection would help disentangle vaccine- and infection-induced immunity.

Interim 2023/24 influenza A vaccine effectiveness: VEBIS European primary care and hospital multicentre studies, September 2023 to January 2024.

Influenza A viruses circulated in Europe from September 2023 to January 2024, with influenza A(H1N1)pdm09 predominance. We provide interim 2023/24 influenza vaccine effectiveness (IVE) estimates from two European studies, covering 10 countries across primary care (EU-PC) and hospital (EU-H) settings. Interim IVE was higher against A(H1N1)pdm09 than A(H3N2): EU-PC influenza A(H1N1)pdm09 IVE was 53% (95% CI: 41 to 63) and 30% (95% CI: -3 to 54) against influenza A(H3N2). For EU-H, these were 44% (95% CI: 30 to 55) and 14% (95% CI: -32 to 43), respectively.

Influenza vaccine effectiveness in Europe: Results from the 2022-2023 VEBIS (Vaccine Effectiveness, Burden and Impact Studies) primary care multicentre study.

Background: Influenza A(H3N2) viruses dominated early in the 2022-2023 influenza season in Europe, followed by higher circulation of influenza A(H1N1)pdm09 and B viruses. The VEBIS primary care network estimated the influenza vaccine effectiveness (VE) using a multicentre test-negative study. Materials and Methods: Primary care practitioners collected information and specimens from patients consulting with acute respiratory infection. We measured VE against any influenza, influenza (sub)type and clade, by age group, by influenza vaccine target group and by time since vaccination, using logistic regression. Results: We included 38 058 patients, of which 3786 were influenza A(H3N2), 1548 influenza A(H1N1)pdm09 and 3275 influenza B cases. Against influenza A(H3N2), VE was 36% (95% CI: 25-45) among all ages and ranged between 30% and 52% by age group and target group. VE against influenza A(H3N2) clade 2b was 38% (95% CI: 25-49). Overall, VE against influenza A(H1N1)pdm09 was 46% (95% CI: 35-56) and ranged between 29% and 59% by age group and target group. VE against influenza A(H1N1)pdm09 clade 5a.2a was 56% (95% CI: 46-65) and 79% (95% CI: 64-88) against clade 5a.2a.1. VE against influenza B was 76% (95% CI: 70-81); overall, 84%, 72% and 71% were among 0-14-year-olds, 15-64-year-olds and those in the influenza vaccination target group, respectively. VE against influenza B with a position 197 mutation of the hemagglutinin (HA) gene was 79% (95% CI: 73-85) and 90% (95% CI: 85-94) without this mutation. Conclusion: The 2022-2023 end-of-season results from the VEBIS network at primary care level showed high VE among children and against influenza B, with lower VE against influenza A(H1N1)pdm09 and A(H3N2).

Comparison of heat-illness associations estimated with different temperature metrics in the Australian Capital Territory, 2006-2016.

While the associations of heat with health outcomes is well researched, there is less consensus on the measures used to define heat exposure and the short-term and delayed impacts of different temperature metrics on health outcomes. We investigate the nonlinear and short-term relationship of three temperature metrics and reported incidence of three gastrointestinal illnesses: salmonellosis, campylobacteriosis and cryptosporidiosis in the Australian Capital Territory (ACT). We also examine the nonlinear association of these illnesses with extreme heat (5th, 75th, 90th percentile of all heat measures). Generalized linear models with Poisson regression accounting for overdispersion, seasonal and long-term trend, weekly number of outbreaks and rainfall were developed for mean and maximum weekly temperature and the heat stress index (EHIaccl). Bacterial illnesses (salmonellosis and campylobacteriosis) showed an overall positive association with extreme heat (75th and 90th percentile of all three heat measures) and an inverse association with low temperature (5th percentile). The shape of the exposure-response curve across a range of temperatures and the lagged effects varied for each disease. Modelling the short-term and delayed effects of heat using different metrics across a range of illnesses can help identify the most appropriate measure to inform local public health intervention planning for heat-related emergencies.

Effectiveness of parental cocooning as a vaccination strategy to prevent pertussis infection in infants: A case-control study.

BACKGROUND: During a pertussis epidemic in 2009, the Department of Health, Victoria, Australia, implemented a cocoon program offering parents of new babies a funded-dose of pertussis-containing vaccine. We assessed vaccine effectiveness (VE) of the program in reducing pertussis infection in infants. METHODS: Using a matched case-control design, infants aged <12 months that were notified with pertussis between 1 January 2010 and 31 December 2011, and born during the time that the cocoon program was in place, were identified. Controls were matched by area of residence and date of birth. Telephone interviews we conducted to ascertain parents' vaccination status, and if vaccinated, timing of vaccination receipt relative to the birth of their baby. Odds ratios (ORs) were calculated for the association between vaccination and pertussis infection, with VE calculated as (1 - OR) × 100%. RESULTS: The study recruited 215 cases and 240 controls (response rates 67% and 25% of eligible participants, respectively). Vaccination of both parents after delivery of the infant and ≥28 days prior to illness onset reduced pertussis infection by 77% (Vaccine Effectiveness [VE] = 77% (confidence interval [95% CI], 18-93%). After adjusting for maternal education, presence of a sibling within the household, and the infants' primary course vaccination status, the adjusted VE was 64% (95% CI, -58-92%). CONCLUSIONS: Although not reaching statistical significance, our results demonstrated that cocoon immunisation - where both parents are vaccinated in the post-partum period - may offer some protection again infant pertussis infection. Cocoon immunisation could be considered in circumstances where antenatal vaccination of the mother has not occurred.

Diagnostic testing in influenza and pertussis related paediatric intensive care unit admissions,Queensland, Australia, 1997-2013.

Severe respiratory infections make up a large proportion of Australian paediatric intensive care unit (ICU) admissions each year. Identification of the causative pathogen is important and informs clinical management. We investigated the use of polymerase chain reaction (PCR) in the ICU-setting using data collated by the Australian and New Zealand Paediatric Intensive Care (ANZPIC) Registry from five ICUs in Queensland, Australia. We describe diagnostic testing use among pertussis and influenza-related paediatric ICU admissions between 01 January 1997 and 31 December 2013.

The epidemiology of tuberculosis in the Australia Capital Territory, 2006-2015.

AIM: To review the epidemiology of tuberculosis (TB) in the Australian Capital Territory (ACT) over a 10 year period. Methods: A retrospective analysis of the ACT TB notification data from 1 January 2006 to 31 December 2015 was conducted. RESULTS: Over the 10 year study period there were 171 TB notifications in the ACT, with an increasing trend in the number of notifications over time. The median age of cases was 36 years (range 14 to 91 years) and 53.8% of cases were male. Most TB cases (84.2%) were born overseas. Among Australian-born cases the most common risk factor for acquiring TB was close/household contact with a known case of TB (30.8%). The most common risk factor in the overseas-born population was past travel or residence in a high-risk country (86.9%). Of all the TB cases notified, 82.4% successfully completed treatment. CONCLUSION: There was an increasing trend in the number of TB notifications in the ACT over the study period. The highest rate of TB notifications remained in the overseas-born population; with other studies suggesting this is commonly due to reactivation of latent tuberculosis infection (LTBI). As Australia starts working towards TB elimination, options for the screening and management of LTBI, especially in high risk populations, need to be explored.

Pertussis Seasonality Evident in Polymerase Chain Reaction and Serological Testing Data, Queensland, Australia.

We investigated the seasonality of pertussis in Queensland, Australia, between 2008 and 2011 using notification and laboratory data. Polymerase chain reaction and serology testing data demonstrate that in the vaccine era, pertussis remains a seasonal illness, with annual peaks in summer months, and that the seasonality of notification data is masked by testing trends.

Epidemiology of pertussis-related paediatric intensive care unit (ICU) admissions in Australia, 1997-2013: an observational study.

OBJECTIVE: To review the epidemiology of pertussis-related intensive care unit (ICU) admissions across Australia, over a 17-year period. DESIGN: Retrospective descriptive study. SETTING: Australian ICUs contributing data to the Australian and New Zealand Paediatric Intensive Care (ANZPIC) Registry. The number of contributing ICUs increased over the study period, from 8 specialist paediatric ICUs in 1997 to 8 specialist paediatric and 13 general ICUs in 2013. PARTICIPANTS: All paediatric (<16 years) ICU admissions, coded as pertussis-related, between 1 January 1997 and 31 December 2013. RESULTS: A total of 373 pertussis-coded ICU admissions were identified in the ANZPIC Registry over the study period. Of these cases, 52.8% occurred during the 4 years of the recent Australian epidemic (2009-2012). ICU admissions were most likely to occur in infants aged younger than 6 weeks (41.8%, n=156) and aged 6 weeks to 4 months (42.9%, n=160). The median length of stay for pertussis-related ICU admissions was 3.6 days, with 77.5% of cases staying in ICU for <7 days. Approximately half of all admissions (54.8%) required some form of respiratory support, with 32.7% requiring invasive respiratory support. Over the study period, 23 deaths were recorded (6.2% of pertussis-related ICU admissions), of which 20 (87.0%) were infants <4 months old. CONCLUSIONS: Pertussis-related ICU admissions occur primarily in infants too young to be fully protected from active immunisation. More needs to be done to protect these high-risk infants, such as maternal immunisation.

Epidemiology of Australian Influenza-Related Paediatric Intensive Care Unit Admissions, 1997-2013.

BACKGROUND: Influenza virus predictably causes an annual epidemic resulting in a considerable burden of illness in Australia. Children are disproportionately affected and can experience severe illness and complications, which occasionally result in death. METHODS: We conducted a retrospective descriptive study using data collated in the Australian and New Zealand Paediatric Intensive Care (ANZPIC) Registry of influenza-related intensive care unit (ICU) admissions over a 17-year period (1997-2013, inclusive) in children <16 years old. National laboratory-confirmed influenza notifications were used for comparison. RESULTS: Between 1997 and 2013, a total of 704 influenza-related ICU admissions were recorded, at a rate of 6.2 per 1,000 all-cause ICU admissions. Age at admission ranged from 0 days and 15.9 years (median = 2.1 years), with 135 (19.2%) aged <6 months. Pneumonia/pneumonitis and bronchiolitis were the most common primary diagnoses among influenza-related admissions (21.9% and 13.6%, respectively). More than half of total cases (59.2%) were previously healthy (no co-morbidities recorded), and in the remainder, chronic lung disease (16.7%) and asthma (12.5%) were the most common co-morbidities recorded. Pathogen co-detection occurred in 24.7% of cases, most commonly with respiratory syncytial virus or a staphylococcal species. Median length of all ICU admissions was 3.2 days (range 2.0 hours- 107.4 days) and 361 (51.3%) admissions required invasive respiratory support for a median duration of 4.3 days (range 0.2 hours- 107.5 days). There were 27 deaths recorded, 14 (51.9%) in children without a recorded co-morbidity. CONCLUSION: Influenza causes a substantial number of ICU admissions in Australian children each year with the majority occurring in previously healthy children.

The risk of fever following one dose of trivalent inactivated influenza vaccine in children aged ≥6 months to <36 months: a comparison of published and unpublished studies.

There are limited summary data published on the risk of fever and febrile seizures in children following influenza vaccination. We performed a review of the risk of fever and febrile seizures following receipt of trivalent inactivated influenza vaccine (TIV) in children aged ≥6 months to <36 months, searching PubMED and Google Scholar for English language articles from 2000 onwards, and initiated or ongoing unpublished studies since September 2007 using Clinicaltrials.gov. Exclusions included other vaccine co-administration, missing ages or participant numbers, or unmeasured fever. We reviewed articles and collated results using a standard data extraction template. We identified a total of 909 published papers and unpublished trials from a search conducted on 23 January 2013, 669 from Google Scholar, 114 from PubMed and 126 from the Clinicaltrials.gov online database. After excluding 890 published papers or unpublished trials, 5 published papers and 14 unpublished trials were included in this review. Extracted data on number of events, children at risk and time of follow-up were converted to the risk of fever, which was averaged per week of follow-up (referred to as 'averaged weekly risk'). Following one dose of TIV, the median averaged weekly risk of any fever (≥37.5°C) was 26.0% (range 10.3-70.0%) in unpublished trials compared to 8.2% (range 5.3-28.3%) in published papers (p=0.04). The median averaged weekly risk of severe fever (≥39.0°C) was 3.2% (range 0-10.0%) and 2.0% (range 0.6-17.0%), respectively (p=0.91). Variation in the reporting of fever by participant age groups, time since vaccination and the definition or measurement of fever resulted in a wide range of risk estimates. Reporting of febrile reactions should be standardised to allow comparison between manufacturers and influenza seasons.

Sevenfold rise in likelihood of pertussis test requests in a stable set of Australian general practice encounters, 2000-2011.

OBJECTIVE: To better understand the role that diagnostic test-ordering behaviour of general practitioners has on current pertussis epidemiology in Australia. DESIGN AND SETTING: Analysis of Australian general practice encounter data (from the Bettering the Evaluation and Care of Health [BEACH] program) on 13 "pertussis-related problem" (PRP) codes that were most likely to result in a pertussis laboratory test request and Australian pertussis notifications data (from the National Notifiable Diseases Surveillance System [NNDSS]) for the period April 2000 to March 2011. MAIN OUTCOME MEASURES: The change in the proportion of PRP general practice encounters with a pertussis test request between 2000 and 2011, and the change in national pertussis notifications over the same period. RESULTS: The proportion of PRP encounters resulting in a pertussis test request increased from 0.25% between April 2000 and March 2004 to 1.71% between April 2010 and March 2011 (odds ratio, 7.0; 95% CI, 5.5-8.8). The BEACH data on pertussis testing and NNDSS data on pertussis notifications were highly correlated (r = 0.99), and the notification data mirrored the likelihood of a pertussis test request in general practice. The proportion of NNDSS pertussis notifications with a polymerase chain reaction (PCR)-confirmed diagnosis increased from 16.3% between April 2000 and March 2004 to 65.3% between April 2010 and March 2011. CONCLUSION: An increase in pertussis testing following recognition of early epidemic cases may have led to identification of previously undetected infections, resulting in a further increase in notified disease and awareness among GPs. The changing likelihood of being tested may also be due to expanding availability and use of PCR testing in Australia.

Continued dominance of pandemic A(H1N1) 2009 influenza in Victoria, Australia in 2010.

The 2010 Victorian influenza season was characterized by normal seasonal influenza activity and the dominance of the pandemic A(H1N1) 2009 strain. General Practice Sentinel Surveillance rates peaked at 9.4 ILI cases per 1000 consultations in week 36 for metropolitan practices, and at 10.5 ILI cases per 1000 in the following week for rural practices. Of the 678 ILI cases, 23% were vaccinated, a significantly higher percentage than in previous years. A significantly higher percentage of ILI patients were swabbed in 2010 compared to 2003-2008, but similar to 2009, with a similar percentage being positive for influenza as in previous years. Vaccination rates increased with patient age. Melbourne Medical Deputising Service rates peaked in week 35 at 19.1 ILI cases per 1000 consultations. Of the 1914 cases of influenza notified to the Department of Health, Victoria, 1812 (95%) were influenza A infections - 1001 (55%) pandemic A(H1N1) 2009, 4 (< 1%) A(H3N2) and 807 (45%) not subtyped; 88 (5%) were influenza B; and 14 (< 1%) were influenza A and B co-infections. The World Health Organization Collaborating Centre for Reference and Research on Influenza tested 403 isolates of which 261 were positive for influenza, 250 of which were influenza A and 11 were influenza B. Ninety-two per cent of the influenza A viruses were pandemic A(H1N1) 2009, and following antigenic analysis all of these were found to be similar to the current vaccine strain. Three viruses (0.9%) were found to be oseltamivir resistant due to an H275Y mutation in the neuraminidase gene.

Australia's notifiable disease status, 2008: annual report of the National Notifiable Diseases Surveillance System.

In 2008, 65 communicable diseases and conditions were nationally notifiable in Australia. States and territories reported a total of 160,508 notifications of communicable diseases to the National Notifiable Diseases Surveillance System, an increase of 9% on the number of notifications in 2007. In 2008, the most frequently notified diseases were sexually transmissible infections (69,459 notifications, 43% of total notifications), vaccine preventable diseases (34,225 notifications, 21% of total notifications) and gastrointestinal diseases (27,308 notifications, 17% of total notifications). There were 18,207 notifications of bloodborne diseases; 8,876 notifications of vectorborne diseases; 1,796 notifications of other bacterial infections; 633 notifications of zoonoses and 4 notifications of quarantinable diseases.

Annual report of the National Influenza Surveillance Scheme, 2008.

The 2008 influenza season was moderate overall, with fewer laboratory-confirmed cases and influenza-like illness (ILI) presentations than in 2007, which was the most severe influenza season since national reporting of influenza began in 2001. In 2008, the number of laboratory-confirmed notifications for influenza was 1.9 times higher than the 5-year mean. High notification rates were reflected in an increase in presentations with ILI to sentinel general practices and emergency departments. Notification rates were highest in the 0-4 year age group. Unusually, the season was predominantly due to influenza B, with 54% of notifications being influenza B and 43% being influenza A (3% type unknown). The rate of influenza B was higher among the younger age groups, compared with influenza A, which was more common in the older age groups. Of influenza viruses circulating during the 2008 season, A(H3) viruses were predominant and were antigenically similar to the 2008 A(H3) vaccine strain, while the majority of A(H1) strains showed significant drift away from the 2008 A(H1) vaccine strain. There were approximately equal proportions of viruses from the 2 influenza B lineages B/Yamagata and B/Victoria.

Australia's notifiable diseases status, 2006: annual report of the National Notifiable Diseases Surveillance System.

In 2006, 66 diseases and conditions were nationally notifiable in Australia. States and territories reported a total of 138,511 cases of communicable diseases to the National Notifiable Diseases Surveillance System: an increase of 10.4% on the number of notifications in 2005. In 2006, the most frequently notified diseases were sexually transmissible infections (57,941 notifications, 42% of total notifications), gastrointestinal diseases (27,931 notifications, 20% of total notifications) and vaccine preventable diseases (22,240 notifications, 16% of total notifications). There were 19,111 notifications of bloodborne diseases; 8,606 notifications of vectorborne diseases; 1,900 notifications of other bacterial infections; 767 notifications of zoonoses and 3 notifications of quarantinable diseases.

Annual report of the National Influenza Surveillance Scheme, 2007.

The year 2007 saw the most severe influenza season since national reporting of influenza began in 2001. Early in the season the National Incident Room was activated to provide effective national surveillance, reporting and management of the 2007 seasonal influenza outbreak. A surveillance team were tasked with establishing enhanced surveillance for the 2007 season and investigating unusual events in this outbreak. Key data required to comprehensively describe the number of cases, morbidity, mortality and virology of the influenza outbreak and the possible sources of these data were identified. In 2007 the number of laboratory-confirmed notifications for influenza was 3.1 times higher than the five-year mean. Forty-four per cent of notifications occurred in Queensland. High notification rates were reflected in an increase in presentations with influenza-like illness to sentinel general practices and Emergency Departments. Notifications and notification rates were highest in the 0-4 and 5-9 years age groups, possibly due to a bias towards testing in these age groups. The clinical morbidity of the infection in terms of complications or most affected groups cannot be determined but anecdotal reports indicate this season may have impacted young adults more than is usual. The available data suggest influenza has caused a significant burden on workplaces and the health care system as indicated by data on absenteeism and presentations for health care. The proportion of H1 strains of influenza circulating varied across Australia but was higher than 2006 in most jurisdictions. In 2007, 1,406 influenza isolates from Australia were antigenically analysed at the World Health Organization Collaborating Centre for Reference and Research on Influenza in Melbourne: 58.7% were A(H3N2), 34.4% were A(H1N1) and 6.9% were influenza B viruses. Antigenic drift away from the vaccine strain A/Wisconsin/67/2005 was observed with the A(H3N2) viruses and was also seen with most of the A(H1N1) viruses when compared with the vaccine strain A/New Caledonia/20/99. The small number of influenza B viruses examined were predominately of the B/Yamagata-lineage. Monitoring influenza through the National Incident Room during the 2007 season offered an excellent opportunity to conduct enhanced surveillance under conditions that were real and potentially serious but not an emergency. It enabled the current state of our surveillance systems to be assessed and opportunities for improvement to be identified.