Laboratory-confirmed Influenza Cases Research Articles

Mid-Term Estimates of Influenza Vaccine Effectiveness against the A(H1N1)pdm09 Prevalent Circulating Subtype in the 2023/24 Season: Data from the Sicilian RespiVirNet Surveillance System.

The current influenza season started in Italy in October 2023, approaching the epidemic peak in late December (52nd week of the year). We aimed to explore the mid-term virologic surveillance data of the 2023/2024 influenza season (from 16 October 2023 to 7 January 2024) in Sicily, the fourth most populous Italian region. A test-negative design was used to estimate the effectiveness of seasonal influenza vaccine (VE) against A(H1N1)pdm09 virus, the predominant subtype in Sicily (96.2% of laboratory-confirmed influenza cases). Overall, 29.2% (n = 359/1230) of oropharyngeal swabs collected from patients with influenza-like illness (ILI) were positive for influenza. Among the laboratory-confirmed influenza cases, 12.5% (n = 45/359) were vaccinated against influenza, with higher prevalence of laboratory-confirmed diagnosis of influenza A among subjects vaccinated with quadrivalent inactivated standard dose (29.4%), live attenuated intranasal (25.1%), and quadrivalent inactivated high-dose (23.8%) influenza vaccines. Comparing influenza vaccination status for the 2023/2024 season among laboratory-confirmed influenza-positive and -negative samples, higher vaccination rates in influenza-negative samples (vs. positive) were observed in all age groups, except for 45-64 years old, regardless of sex and comorbidities. The overall adjusted VE (adj-VE) was 41.4% [95%CI: 10.5-61.6%], whereas the adj-VE was 37.9% [95%CI: -0.7-61.7%] among children 7 months-14 years old and 52.7% [95%CI: -38.0-83.8%] among the elderly (≥65 years old).

Assessing Influenza Vaccine Adherence Among Pregnant Women: A Health Center-Based Study in Qatar

The World Health Organization (WHO) issues recommendations regarding influenza vaccine utilization, with a focus on safeguarding the most vulnerable and high-risk segments of the population against severe disease [1]. WHO's policy report on influenza vaccine, published in 2022, specifically designates pregnant women as a priority group for nations expanding their influenza vaccination initiatives, underlining the vaccine's capacity to confer protection to both mothers and their newborns for up to six months postpartum, shielding them from influenza infections [2]. Extensive evidence attests to the safety of administering influenza vaccines to pregnant women, with studies revealing a substantial reduction in laboratory-confirmed influenza cases, ranging from 35% to 70% for mothers and 28% to 61% for infants under six months of age [3,5]. The Ministry of Public Health (MOPH) in Qatar recommends that pregnant women receive a single dose of the influenza vaccine during any trimester of pregnancy, and this guidance is implemented across Antenatal clinics, including the Rawadat al Khail Health Center. Adherence to both local and WHO guidelines in clinical practice is of paramount importance. Thus, this study endeavors to ascertain the degree of adherence exhibited by healthcare professionals and pregnant women to the recommendations pertaining to influenza vaccination during pregnancy.

Sentinel Surveillance of Severe Acute Respiratory Infections in Serbia in 2022-2023 Season

Abstract Introduction Sentinel surveillance of severe acute respiratory infections (SARI) was implemented in Serbia in November 2009. Nine sentinel hospitals in 3 cities participated in the integrated SARI surveillance system. Four of them are children's hospitals. The aim of this study is to provide a review of integrated sentinel surveillance of SARI in Serbia in 2022-2023 influenza season, from October 2022 to April 2023. Methods Integrated Sentinel Surveillance of SARI has been done in accordance with professional guidance for epidemiological surveillance of influenza. Both epidemiological and virological data were collected on a weekly basis. All specimens were tested for influenza, SARS-CoV-2 and Respiratory syncytial virus (RSV). Intensive care units (ICUs), pediatric and respiratory disease wards were all represented. For laboratory confirmation, Real time polymerase chain reaction (RT-PCR) was used. Results Start of influenza season was registered in week 44/2022. A total of 3027 SARI cases were reported with 100% recorded age. Of these, 14% were 0-4 years old, 9% were 5-14, 7% were 15-29, 38% were 30-64 and 32% were ≥65. Among these cases, 607(20%) respiratory specimens were collected during the surveillance period. The number of positive samples for influenza was 208(34%), for SARS-CoV-2 was 37(6%) and for RSV 12(2%). The highest proportion of laboratory-confirmed influenza cases was 58% in week 51/2022. then, above 50% in week 7/2023 and 8/2023. All three influenza viruses were confirmed: A(H1)pdm09, A(H3) and type B. B viruses predominated, accounting for 38% of all sentinel SARI detections. There no were death associated to influenza, SARS-CoV-2 and RSV. Conclusions Integration epidemiological with laboratory surveillance as well as integrated sentinel SARI surveillance for influenza, SARS -CoV-2 and RSV highlights the importance of maintaining and improving national influenza surveillance capacity especially in the frame of International Health Regulations. Key messages • Quality, representativeness and sustainability are the guiding principles for integrated, SARS-CoV-2, RSV and influenza sentinel SARI surveillance. • The threat of influenza remains, and it is essential for countries to be vigilant for the emergence of non seasonal influenza viruses of pandemic potential and prepare for the next influenza season.

Influenza Vaccine Effectiveness in Preventing Laboratory-Confirmed Influenza Cases and Hospitalizations in Navarre, Spain, 2022-2023.

We estimated influenza vaccine effectiveness (IVE) in preventing outpatient and hospitalized cases in the 2022-2023 season. A test-negative design included a representative sample of outpatients and all hospitalized patients with influenza-like illness (ILI) from October 2022 to May 2023 in Navarre, Spain. ILI patients were tested by PCR for influenza virus. Influenza vaccination status was compared between confirmed influenza cases and test-negative controls. Among 3321 ILI patients tested, IVE to prevent influenza cases was 34% (95% confidence interval (CI): 16 to 48) overall, 85% (95%CI: 63 to 94) against influenza B, and 28% (95%CI: 3 to 46) against A(H3N2). Among 558 outpatients, 222 (40%) were confirmed for influenza: 55% A(H3N2), 11% A(H1N1), and 31% B. Overall, IVE to prevent outpatient cases was 48% (95%CI: 8 to 70), 88% (95%CI: 3 to 98) against influenza B, and 50% (95%CI: -4 to 76) against A(H3N2). Of 2763 hospitalized patients, 349 (13%) were positive for influenza: 64% A(H3N2), 17% A(H1N1), and 8% B. IVE to prevent hospitalization was 24% (95%CI: -1 to 42) overall, 82% (95%CI: 49 to 93) against influenza B, and 16% (95%CI: -17 to 40) against A(H3N2). No IVE was observed in preventing influenza A(H1N1). IVE was high to prevent influenza B, moderate against A(H3N2) and null against A(H1N1). A lower proportion of influenza B cases may explain the smaller IVE in hospitalized patients than in outpatients. The null IVE against A(H1N1) was consistent with the observed antigenic drift and supports the new composition of the 2023-2024 influenza vaccine.

Changes in epidemic intensity of influenza during 2014-2020 in Shanghai

Objective: To evaluate the performance of the influenza surveillance network and compare the epidemic intensity of influenza during 2014-2020 in Shanghai. Methods: Based on the weekly reports of influenza-like illness (ILI) and laboratory-confirmed influenza cases from January 1, 2014 to December 31, 2020. This study first evaluated the data reporting and specimen collection of ILI cases for each sentinel hospital, and then calculated the percentage of ILI (ILI%), the proportion of specimens tested positive for influenza, and the incidence of influenza among all ILI outpatient and emergency visits to measure the epidemic intensity of influenza. Finally, seasonal autoregressive integrated moving average (ARIMA) model was applied to quantify the changes in epidemic intensity of influenza in 2020. Results: The proportion of influenza surveillance sentinel hospitals with a score of less than 5 in the evaluation of ILI data reporting and samples collection were 9.68% and 21.05% in 2020 in Shanghai, respectively. ILI% was estimated to be 1.51% (95%CI: 1.50%-1.51%) and 2.31% (95%CI: 2.30%-2.32%), respectively for 2014-2019 and 2020; the proportion of specimens tested positive was 24.27% (95%CI: 24.02%- 24.51%) and 7.15% (95%CI: 6.78%-7.54%), respectively; and the incidence of influenza was 3.66‰ (95%CI: 3.62‰-3.70‰) and 1.65‰ (95%CI: 1.57‰-1.74‰), respectively. ARIMA model showed that ILI% was increased by 45.25% in 2020 in Shanghai, and the proportion of specimens tested positive and the incidence of influenza were reduced by 78.45% and 51.80%, respectively. Conclusions: In 2020, the performance of influenza surveillance system has changed, ILI% has increased, the proportion of specimens tested positive and the incidence of influenza has decreased in Shanghai. The change in the quality of influenza surveillance is also a potential factor affecting the epidemic intensity of influenza. In the future, the quality control of influenza surveillance network still needs to be further strengthened.

Moderately Low Effectiveness of the Influenza Quadrivalent Vaccine: Potential Mismatch between Circulating Strains and Vaccine Strains.

The annual seasonal influenza vaccination is the most effective way of preventing influenza illness and hospitalization. However, the effectiveness of influenza vaccines has always been controversial. Therefore, we investigated the ability of the quadrivalent influenza vaccine to induce effective protection. Here we report strain-specific influenza vaccine effectiveness (VE) against laboratory-confirmed influenza cases during the 2019/2020 season, characterized by the co-circulation of four different influenza strains. During 2019-2020, 778 influenza-like illness (ILI) samples were collected from 302 (39%) vaccinated ILI patients and 476 (61%) unvaccinated ILI patients in Riyadh, Saudi Arabia. VE was found to be 28% and 22% for influenza A and B, respectively. VE for preventing A(H3N2) and A(H1N1)pdm09 illness was 37.4% (95% CI: 43.7-54.3) and 39.2% (95% CI: 21.1-28.9), respectively. The VE for preventing influenza B Victoria lineage illness was 71.7% (95% CI: -0.9-3), while the VE for the Yamagata lineage could not be estimated due to the limited number of positive cases. The overall vaccine effectiveness was moderately low at 39.7%. Phylogenetic analysis revealed that most of the Flu A genotypes in our dataset clustered together, indicating their close genetic relatedness. In the post-COVID-19 pandemic, flu B-positive cases have reached three-quarters of the total number of influenza-positive cases, indicating a nationwide flu B surge. The reasons for this phenomenon, if related to the quadrivalent flu VE, need to be explored. Annual monitoring and genetic characterization of circulating influenza viruses are important to support Influenza surveillance systems and to improve influenza vaccine effectiveness.

Determining meteorologically-favorable zones for seasonal influenza activity in Hong Kong.

Investigations of simple and accurate meteorology classification systems for influenza epidemics, particularly in subtropical regions, are limited. To assist in preparing for potential upsurges in the demand on healthcare facilities during influenza seasons, our study aims to develop a set of meteorologically-favorable zones for epidemics of influenza A and B, defined as the intervals of meteorological variables with prediction performance optimized. We collected weekly detection rates of laboratory-confirmed influenza cases from four local major hospitals in Hong Kongbetween 2004 and 2019. Meteorological and air quality records for hospitals were collected from their closest monitoring stations. We employed classificationandregression trees to identify zones that optimize the prediction performance of meteorological data in influenza epidemics, defined as a weekly rate > 50th percentile over a year. According to the results, a combination of temperature > 25.1℃ and relative humidity > 79% was favorable to epidemics in hot seasons, whereas either temperature < 16.4℃ or a combination of < 20.4℃ and relative humidity > 76% was favorable to epidemics in cold seasons. The area under the receiver operating characteristic curve (AUC) in model training achieved 0.80 (95% confidence interval [CI], 0.76-0.83) and was kept at 0.71 (95%CI, 0.65-0.77) in validation. The meteorologically-favorable zones for predicting influenza A or A and B epidemics together were similar, but the AUC for predicting influenza B epidemics was comparatively lower. In conclusion, we established meteorologically-favorable zones for influenza A and B epidemics with a satisfactory prediction performance, even though the influenza seasonality in this subtropical setting was weak and type-specific.

Influenza virus subtype/lineage-specific seasonal patterns and age-related infection risk, in Eastern China.

Differences in seasonal pattern and age-related infection risk have been reported between Influenza type A and B, but have not been elaborated at subtype/lineage level. All laboratory-confirmed influenza cases reported in the influenza surveillance system of Jiangsu Province, China from January 2011 to August 2019 were analyzed. Influenza seasonality was characterized using the Seasonal Decomposition method. Binary and multinomial logistic regressions were employed to calculate the odds ratios of influenza subtypes/lineages in relation to age. A total of 28,772 confirmed influenza cases were included. Among them, a majority (64.1%) were influenza A infections. One annual peak was observed for A (H1N1) pdm and B-Yamagata in winter months, and for B-Victoria in spring months, while biannual peaks were observed for A (H3N2) in winter and summer months. Using all ages as the reference, children younger than 5 years and adults of 25-59 years were more likely to infect with A (H1N1) pdm. Older children aged 5-14 years had significantly higher odds of infection with influenza B of both lineages, while individuals aged 15-24 years had higher odds for A (H3N2) and B-Victoria. The elderly (60 years or older) were prone to be infected with A (H3N2) and B-Yamagata. For a specific age group, their likelihood of getting infected with an influenza subtype or lineage was related to the co-circulating influenza subtype or lineage. Influenza viruses have divergent seasonal peak times and age-related infection risk at subtype/lineage level.

Budget Impact Analysis of the Adjuvanted Quadrivalent Influenza Vaccine in the Elderly in Italy

BACKGROUND: Vaccination is the most effective way to prevent influenza and its complications. The MF59-adjuvanted quadrivalent (aQIV) and the high-dose quadrivalent (QIV-HD) influenza vaccines have been specifically developed to protect subjects aged ≥65 years. The aim of this study was to evaluate the economic consequences associated with the use of aQIV in the elderly population in Italy.METHODS: An Excel-based budget impact model was developed to estimate the costs of aQIV for the prevention of influenza and its complications in elderly subjects, from the perspective of the Italian National Health Service. In the base-case analysis a current scenario (with aQIV) was compared with a past scenario (without aQIV), in which only the standard quadrivalent influenza vaccine (QIV-STD) was available. In the scenario analysis, a current scenario was compared with a future (hypothetical) scenario, in which the market share of aQIV grows. Efficacy (or effectiveness) data of vaccines, in terms of reduction of influenza-related deaths and hospitalizations for influenza/pneumonia, respiratory, and cardiac complications, were obtained from the scientific literature. Relative effectiveness of aQIV and QIV-HD vs. QIV-STD in preventing laboratory-confirmed influenza cases came from two meta-analysis of real-world studies. Epidemiological data and unit costs are collected from Italian published sources.RESULTS: In the base-case analysis the introduction of aQIV e QIV-STD was associated with a reduction of influenza and influenza-like illness – ILI (-93,171) cases, hospitalization for influenza, respiratory and cardiovascular complications (-6,823), and deaths (-1,841) and a consequent saving of € 1.9 million and € 24 million related to events and hospital admissions avoided, respectively. In the scenario analysis, the growth of the market shares of aQIV was associated with 13,602 fewer cases of influenza and ILI, 996 fewer hospitalizations, and an overall saving equal to € 3.8 million.CONCLUSIONS: aQIV reduces the number of cases of influenza and ILI, hospitalizations for influenza and respiratory or cardiac complications, and deaths in the Italian population aged ≥65 years.

Capillary Blood Gas in Children Hospitalized Due to Influenza Predicts the Risk of Lower Respiratory Tract Infection.

Background: Influenza may impair respiratory exchange in the case of lower respiratory tract infections (LRTIs). Capillary blood gas (CBG) reflects arterial blood values but is a less invasive method than arterial blood sampling. We aimed to retrospectively verify the usefulness of CBG in pediatric influenza. Material and methods: CBG parameters (pH, pCO2, pO2, SatO2) in laboratory confirmed influenza cases hospitalized in 2013–2020 were verified in terms of LRTI, chest X-ray (CXR) performance, radiologically confirmed pneumonia (CXR + Pneumonia), prolonged hospitalization, and intensive care transfer. A theoretical CBG-based model for CXR performance was created and the odds ratios were compared to the factual CXR performance. Results: Among 409 children (aged 13 days–17 years 3/12, median 31 months), the usefulness of CBG decreased with the age. The SatO2 predicted the LRTI with AUC = 0.74 (95%CI: 0.62–0.86), AUC = 0.71 (0.61–0.82), and AUC = 0.602 (0.502–0.702) in children aged <6 months old (mo), 6–23 mo, 24–59 mo, respectively, while pO2 revealed AUC = 0.73 (0.6–0.85), AUC = 0.67 (0.56–0.78), and AUC = 0.601 (0.501–0.702), respectively. The pCO2 predicted the LRTI most precisely in children <6 months with AUC = 0.75 (0.63–0.87), yet not in older children. A high negative predictive value for CXR + Pneumonia was seen for SatO2 < 6 mo (96.7%), SatO2 6–23 mo (89.6%), pO2 < 6 mo (94.3%), pO2 6–23 mo (88.9%). The use of a CBG-driven CXR protocol (based on SatO2 and pO2) would decrease the odds of an unnecessary CXR in children <2 years old (yo) by 84.15% (74.5–90.14%) and 86.15% (66.46–94.28%), respectively. SatO2 and pO2 also predicted a prolonged hospitalization <6 mo AUC = 0.71 (0.59–0.83) and AUC = 0.73 (0.61–0.84), respectively, and in 6–23 mo AUC = 0.66 (0.54–0.78) and AUC = 0.63 (0.52–0.75), respectively. Conclusions: The CBG is useful mainly in children under two years, predicts the risk of LRTI, and can help exclude the risk of CXR + pneumonia. Children under six months of age represent the group that would benefit the most from CBG. A CBG-based protocol for the performance of CXR could significantly decrease the number of unnecessary CXRs.

Seasonal influenza, its complications and related healthcare resource utilization among people 60 years and older: A descriptive retrospective study in Japan

Evidence suggests that older people aged ≥65 years and those aged 60–64 years with chronic medical conditions are at higher risk of developing severe complications due to influenza virus infection when compared with young, healthy adults. Although seasonal influenza is monitored through a nationwide passive surveillance in Japan, influenza related outcomes and medical resource consumption have not been fully documented. This retrospective database study aimed to describe the epidemiological and clinical characteristics of medically attended influenza cases aged ≥60 years and the associated medical resource consumption in Japan. We used clinically diagnosed influenza (CDI) based on the international classification of disease codes, and laboratory-confirmed influenza (LCI) based on influenza test results, to identify the patient population during a total of nine seasons (2010/2011 to 2018/2019). A total of 372,356 CDI and 31,122 LCI cases were identified from 77 medical institutions. The highest numbers of medically-attended influenza episodes were in patients aged 65–74 years and 75–84 years. On average, across seasons, 5.9% of all-cause hospitalizations were attributable to CDI and 0.4% were LCI. Influenza viruses type A and B co-circulated annually in varying degree of intensity and were associated with similar level of complications, including cardiovascular-related. Oxygen therapy increased with age; by contrast, mechanical ventilation, dialysis, blood transfusion, and intensive care unit admission were higher in the younger groups. In-hospital mortality for inpatients aged ≥ 85 years with CDI and LCI were 18.6% and 15.5%, respectively. Considering the burden associated with medically-attended influenza in this population, influenza prevention, laboratory confirmation and clinical management should be emphasized by general practicians and specialists like cardiologists to protect this aging population.

Severe Influenza-Associated Neurological Disease in Australian Children: Seasonal Population-Based Surveillance 2008-2018.

Influenza-associated neurological disease (IAND) is uncommon but can result in death or neurological morbidity in children. We aimed to describe the incidence, risk factors, and outcome of children with IAND from seasonal influenza in Australia. We analyzed national, population-based, surveillance data for children aged ≤ 14 years with severe influenza and neurological involvement, over 11 Australian influenza seasons, 2008-2018, by the Australian Paediatric Surveillance Unit. There were 633 laboratory-confirmed cases of severe influenza reported. Of these, 165 (26%) had IAND. The average annual incidence for IAND was 3.39 per million children aged ≤ 14 years. Compared to cases without neurological complications, those with IAND were more likely to have a pre-existing neurological disease (odds ratio [OR] 3.03, P < .001), but most children with IAND did not (n = 135, 82%). Children with IAND were more likely to receive antivirals (OR 1.80, P = .002), require intensive care (OR 1.79, P = .001), require ventilation (OR 1.99; P = .001), and die (OR 2.83, P = .004). IAND is a preventable cause of mortality, predominantly in otherwise well children. Incidence estimates validate previous sentinel site estimates from Australia. IAND accounted for a quarter of all severe influenza, is associated with intensive care unit admission, and accounted for half of all influenza deaths.

Age-Specific Estimates of Respiratory Syncytial Virus-Associated Hospitalizations in 6 European Countries: A Time Series Analysis.

Knowledge on age-specific hospitalizations associated with RSV infection is limited due to limited testing, especially in older children and adults in whom RSV infections are not expected to be severe. Burden estimates based on RSV coding of hospital admissions are known to underestimate the burden of RSV. We aimed to provide robust and reliable age-specific burden estimates of RSV-associated hospital admissions based on data on respiratory infections from national health registers and laboratory-confirmed cases of RSV. We conducted multiseason regression analysis of weekly hospitalizations with respiratory infection and weekly laboratory-confirmed cases of RSV and influenza as covariates, based on national health registers and laboratory databases across 6 European countries. The burden of RSV-associated hospitalizations was estimated by age group, clinical diagnosis, and presence of underlying medical conditions. Across the 6 European countries, hospitalizations of children with respiratory infections were clearly associated with RSV, with associated proportions ranging from 28% to 60% in children younger than 3 months and we found substantial proportions of admissions to hospital with respiratory infections associated with RSV in children younger than 3 years. Associated proportions were highest among hospitalizations with ICD-10 codes of "bronchitis and bronchiolitis." In all 6 countries, annual incidence of RSV-associated hospitalizations was >40 per 1000 persons in the age group 0-2 months. In age group 1-2 years the incidence rate ranged from 1.3 to 10.5 hospitalizations per 1000. Adults older than 85 years had hospitalizations with respiratory infection associated to RSV in all 6 countries although incidence rates were low. Our findings highlight the substantial proportion of RSV infections among hospital admissions across different ages and may help public health professionals and policy makers when planning prevention and control strategies. In addition, our findings provide valuable insights for health care professionals attending to both children and adults presenting with symptoms of viral respiratory infections.

How Comorbidities Affect Hospitalization from Influenza in the Pediatric Population.

Influenza is a contagious respiratory illness and can lead to hospitalization and even death. Understanding how comorbidities affect the severity of influenza can help clinical management. The aim of this study is to offer more information about comorbidities that might be associated with the severity of influenza in children. We used a statewide network in Rhode Island, USA, to extract data for laboratory-confirmed influenza cases among children 19 years old or younger. We identified 1169 lab-confirmed influenza cases. The most common comorbidities were asthma (17.1%), neurodevelopmental disorders (10.3%), gastrointestinal disorders (7.6%), atopic dermatitis (7%), and endocrine and metabolic diseases (6.8%). Interestingly, 80.8% (63 out of 78) of children who had an influenza-related hospital admission had at least one comorbidity, and among hospitalized children with influenza, the most common comorbidities were neurological diseases (28.2%, 22/78), gastrointestinal disorders (25.6%, 20/78), endocrine and metabolic diseases (24.4%, 19/78), and neurodevelopmental disorders (23.1%, 18/78). Children with endocrine or metabolic diseases were 8.23 times more likely to be admitted to the hospital, and children with neurological disorders were 6.35 times more likely to be admitted (OR: 8.23, 95% CI: 4.42–15.32 and OR: 6.35, 95% CI: 3.60–11.24, respectively). In summary, we identified specific comorbidities associated with influenza hospitalization and length of hospital stay, and these groups should be prioritized for public health interventions.

A Systematic Review of Influenza Epidemiology and Surveillance in the Eastern Mediterranean and North African Region.

Seasonal influenza represents a huge health burden, resulting in significant mortality and morbidity. Following the 2009 H1N1 pandemic, focus has been directed on the burden of influenza globally. Country and regional disease burden estimates play important roles in helping inform decisions on national influenza intervention programmes. Despite improvements in influenza surveillance following the 2009 pandemic, many opportunities remain unexplored in the Eastern Mediterranean and North African (EMNA) region, which has a high prevalence of patients with chronic disease and thus a population at high risk of influenza complications. We conducted a systematic literature review of Embase, Medline, Scopus and the Cochrane Database of Systematic Reviews from 1 January 1998 to 31 January 2020 covering the EMNA region with the aim to describe the epidemiology of influenza in the region and assess the influenza epidemiological surveillance research landscape. Relevant data on study characteristics, population, clinical/virology characteristics and epidemiology were extracted and summarised descriptively. Of the 112 studies identified for inclusion, 90 were conducted in the Eastern Mediterranean region, 19 in North Africa and three across the EMNA region. Data were reported on 314,058 laboratory-confirmed influenza cases, 96 of which were derived from surveillance systems. Amongst the surveillance studies, the percentage of positive cases reported ranged from 1% to 100%. The predominantly identified influenza strain was strain A; H1N1 was the most prominent circulating subtype. Typing was performed in approximately 75% and subtyping in 50% of studies, respectively. Data on those considered most at risk for influenza complications were collected in 21% of studies, highlighting a regional gap for these data. Our review reveals existing gaps in regional estimates of influenza health and economic burden, hospitalisation rates and duration, and highlights the need for robust and high-quality epidemiology data to help inform public health interventions.Supplementary InformationThe online version contains supplementary material available at 10.1007/s40121-021-00534-3.

Effects of Dust Event Days on Influenza: Evidence from Arid Environments in Lanzhou

Airborne aerosol is believed to be an important pathway for infectious disease transmissions like COVID-19 and influenza. However, the effects of dust event days on influenza have been rarely explored, particularly in arid environments. This study explores the effects of ambient particulate matter (PM) and dust events on laboratory-confirmed influenza in a semi-arid city. A descriptive analysis of daily laboratory-confirmed influenza (influenza) cases, PM (PM10 and PM2.5), meteorological parameters, and dust events were conducted from 2014 to 2019 in Lanzhou, China. The case-crossover design combined with conditional Poisson regression models was used to estimate the lagging effects of PM and dust events on influenza. In addition, a hierarchical model was used to quantitatively evaluate the interactive effect of PM with ambient temperature and absolute humidity on influenza. We found that PM and dust events had a significant effect on influenza. The effects of PM10 and PM2.5 on influenza became stronger as the cumulative lag days increased. The greatest estimated relative risks (RRs) were 1.018 (1.011,1.024) and 1.06 1(1.034,1.087), respectively. Compared with the non-dust days, the effects of dust events with duration ≥ 1 day and with duration ≥ 2 days on influenza were the strongest at lag0 day, with the estimated RRs of 1.245 (95% CI: 1.061-1.463) and 1.483 (95% CI: 1.232-1.784), respectively. Subgroup analysis showed that pre-school children and school-aged children were more sensitive to PM and dust events exposure. Besides, we also found that low humidity and temperature had an interaction with PM to aggravate the risk of influenza. In summary, ambient PM and dust events exposure may increase the risk of influenza, and the risk of influenza increases with the dust events duration. Therefore, more efforts from the government as well as individuals should be strengthened to reduce the effect of PM on influenza, particularly in cold and dry weather.

Influenza A(H3N2) Outbreak on a University Campus - Michigan, October-November 2021.

On November 10, 2021, the Michigan Department of Health and Human Services (MDHHS) was notified of a rapid increase in influenza A(H3N2) cases by the University Health Service (UHS) at the University of Michigan in Ann Arbor. Because this outbreak represented some of the first substantial influenza activity during the COVID-19 pandemic, CDC, in collaboration with the university, MDHHS, and local partners conducted an investigation to characterize and help control the outbreak. Beginning August 1, 2021, persons with COVID-19-like* or influenza-like illness evaluated at UHS received testing for SARS-CoV-2, influenza, and respiratory syncytial viruses by rapid multiplex molecular assay.† During October 6-November 19, a total of 745 laboratory-confirmed influenza cases were identified.§ Demographic information, genetic characterization of viruses, and influenza vaccination history data were reviewed. This activity was conducted consistent with applicable federal law and CDC policy.¶.

Maternal Vaccination Protects Infants Against Flu and Pertussis

Source: Rowe SL, Leder K, Perrett KP, et al. Maternal vaccination and infant influenza and pertussis. Pediatrics. 2021;148(3): e2021051076; doi.10.1542/peds.2021-051076Investigators from multiple institutions in Australia conducted a population-level inception cohort study to assess the effectiveness of maternal influenza and pertussis vaccination during pregnancy in preventing these diseases in their children during the first 6 months of life. For the study, they abstracted data from the Victorian Perinatal Data Collection (VPDC) on women whose pregnancies ended between September 2015 and December 2017. The VPDC includes information on all live births and stillbirths in Victoria, Australia, including demographic and clinical data related to pregnancy and birth. In addition, whether the mother received influenza and/or pertussis vaccine at any time during pregnancy is recorded. Data from multiple databases were reviewed to identify laboratory-confirmed cases of influenza and pertussis in infants <6 months old during the study period and record ED visits, hospital admissions, and deaths from influenza and pertussis. Information from these databases and VPDC were linked to identify mother-infant dyads.The primary study outcomes were laboratory-confirmed cases of influenza and pertussis in infants born to mothers included in the study, and secondary outcomes included cases of severe disease, defined as ED visit, hospitalization, or death from influenza or pertussis in study infants. Poisson regression was used to calculate the relative risk (RR) for influenza and pertussis in infants of mothers vaccinated during pregnancy vs not vaccinated, after adjusting for multiple confounders. Results were stratified in infants <2 months old, and those 2 to <6 months of age. Vaccine effectiveness (VE) of maternal immunization in preventing childhood illness was estimated as (1-RR) × 100.Data were analyzed on 186,962 mother-infant dyads. Overall, 45.9% of study women were vaccinated against influenza during pregnancy and 68.5% against pertussis. There were 185,404 and 184,194 infants, respectively, included in influenza and pertussis vaccination analyzes. The risk of influenza was significantly reduced in children whose mothers were vaccinated, both among children <2 months old (RR, 0.44; 95% CI, 0.25, 0.77), and in those 2 to <6 months of age (RR, 0.64; 95% CI, 0.42, 0.98), with VE estimated as 56.1% (95% CI, 23.3%, 74.9%) and 35.7% (95% CI, 2.2%, 57.7%), respectively. Maternal vaccination reduced the risk of pertussis in infants <2 months old (RR, 0.20; 95% CI, 0.06, 0.63), with an estimated VE of 80.1% (95% CI, 37.1%, 93.7%), but no significant effect was noted among infants 2 to <6 months old (RR, 0.68; 95% CI, 0.33, 1.39). Maternal pertussis immunization reduced the risk of severe pertussis in infants <2 months old (RR, 0.38; 95% CI, 0.16, 0.94). There were no significant effects from maternal vaccination on severe cases of pertussis in children 2 to <6 months old or on influenza among children <6 months old.The authors conclude that maternal vaccination during pregnancy reduces the risk of influenza and pertussis in infants <2 months old.Dr Brady has disclosed no financial relationship relevant to this commentary. This commentary does not contain a discussion of an unapproved/investigative use of a commercial product/device.The goal of maternal immunization is to provide infants with passive antibodies prior to their first dose of vaccines. In a previous study, Baxter et al1 noted that maternal Tdap during pregnancy significantly reduced pertussis risk during the entire first year of life (See AAP Grand Rounds. 2017;38[2]:15.)1 In the current study, which included infants born at ≥30 weeks’ gestation, this benefit was most notable only in infants <2 months. In contrast, Baxter et al1 enrolled only infants born at ≥37 weeks’ gestation, allowing more time for antibody transfer after maternal Tdap receipt (usually between 27–36 weeks’ gestation).2As demonstrated by the results of the current study, maternal vaccination during pregnancy also reduces the infant’s risk for influenza during the first 6 months of life. Tdap and influenza vaccination rates during pregnancy, however, remain suboptimal.3 To assess influenza and Tdap vaccination coverage among women pregnant during the 2020–21 influenza season, the Centers for Disease Control and Prevention (CDC) conducted a survey during April 2021.4 Among 1,795 survey respondents who were pregnant anytime during October 2020–January 2021, 54.5% reported receiving an influenza vaccine before or during pregnancy. Among 729 respondents, 53.5% reported receiving Tdap during pregnancy. Unfortunately, receipt of both influenza and Tdap vaccines was reported by only 30.7% of women.COVID-19 vaccines also are recommended for all pregnant women.5 Providers need to take every opportunity to recommend these vaccines for their pregnant patients.Vaccination of pregnant women with Tdap, influenza, and COVID-19 vaccines is safe and protects the mother and her young infant.As influenza vaccines are approved only for infants ≥6 months of age, the 6-month duration of immunity conferred by maternal influenza vaccination provides further support for maternal immunization.

Incidence of Laboratory-Confirmed Influenza among HIV-Infected versus HIV-Uninfected Individuals in Two Districts of Ghana, 2014 to 2016.

Influenza is known to cause severe respiratory illness in HIV-infected adults, but there are few data describing the relationship between HIV infection and influenza in West African countries such as Ghana. We conducted a prospective cohort study in the Shai-Osudoku and Ningo Prampram districts of Ghana from 2014 to 2016. Beginning May 2014, 266 HIV-infected and 510 HIV-uninfected participants age 18 to 73 years were enrolled and monitored for 12 months. We observed 4 and 11 laboratory-confirmed influenza cases among HIV-infected and HIV-uninfected persons, respectively. The overall rate of laboratory-confirmed influenza among HIV-infected participants was 15.0 per 1,000 person years (PY) (95% CI, 0.3-29.80 per 1,000 PY), whereas that among HIV-uninfected participants was 21.6 per 1,000 PY (95% CI, 8.8-34.3 per 1,000 PY) (incidence density ratio, 0.70; P = 0.56). Our study found no significant difference in the incidence of laboratory-confirmed influenza-associated illness among HIV-infected and HIV-uninfected individuals in Ghana.

Influenza Vaccine Effectiveness in Preventing Severe Outcomes in Patients Hospitalized with Laboratory-Confirmed Influenza during the 2017-2018 Season. A Retrospective Cohort Study in Catalonia (Spain).

Seasonal influenza is a common cause of hospital admission, especially in older people and those with comorbidities. The objective of this study was to determine influenza vaccine effectiveness (VE) in preventing intensive care admissions and shortening the length of stay (LOS) in hospitalized laboratory-confirmed influenza cases (HLCI) in Catalonia (Spain). A retrospective cohort study was carried out during the 2017–2018 season in HLCI aged ≥18 years from 14 public hospitals. Differences in means and proportions were assessed using a t-test or a chi-square test as necessary and the differences were quantified using standardized effect measures: Cohen’s d for quantitative and Cohen’s w for categorical variables. Adjusted influenza vaccine effectiveness in preventing severity was estimated by multivariate logistic regression where the adjusted VE = (1 − adjusted odds ratio) · 100%; adjustment was also made using the propensity score. We analyzed 1414 HLCI aged ≥18 years; 465 (33%) were vaccinated, of whom 437 (94%) were aged ≥60 years, 269 (57.8%) were male and 295 (63.4%) were positive for influenza type B. ICU admission was required in 214 (15.1%) cases. There were 141/1118 (12.6%) ICU admissions in patients aged ≥60 years and 73/296 (24.7%) in those aged <60 years (p < 0.001). The mean LOS and ICU LOS did not differ significantly between vaccinated and unvaccinated patients. There were 52/465 (11.2%) ICU admissions in vaccinated cases vs. 162/949 (17.1%) in unvaccinated cases. Patients admitted to the ICU had a longer hospital LOS (mean: 22.4 [SD 20.3] days) than those who were not (mean: 11.1 [SD 14.4] days); p < 0.001. Overall, vaccination was associated with a lower risk of ICU admission. Taking virus types A and B together, the estimated adjusted VE in preventing ICU admission was 31% (95% CI 1–52; p = 0.04). When stratified by viral type, the aVE was 40% for type A (95% CI -11–68; p = 0.09) and 25% for type B (95% CI -18–52; p = 0.21). Annual influenza vaccination may prevent ICU admission in cases of HLCI. A non-significantly shorter mean hospital stay was observed in vaccinated cases. Our results support the need to increase vaccination uptake and public perception of the benefits of influenza vaccination in groups at a higher risk of hospitalization and severe outcomes.