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).

Influenza vaccine effectiveness against influenza A subtypes in Europe: Results from the 2021-2022 I-MOVE primary care multicentre study.

BACKGROUND: In 2021-2022, influenza A viruses dominated in Europe. The I-MOVE primary care network conducted a multicentre test-negative study to measure influenza vaccine effectiveness (VE). METHODS: Primary care practitioners collected information on patients presenting with acute respiratory infection. Cases were influenza A(H3N2) or A(H1N1)pdm09 RT-PCR positive, and controls were influenza virus negative. We calculated VE using logistic regression, adjusting for study site, age, sex, onset date, and presence of chronic conditions. RESULTS: Between week 40 2021 and week 20 2022, we included over 11 000 patients of whom 253 and 1595 were positive for influenza A(H1N1)pdm09 and A(H3N2), respectively. Overall VE against influenza A(H1N1)pdm09 was 75% (95% CI: 43-89) and 81% (95% CI: 45-93) among those aged 15-64 years. Overall VE against influenza A(H3N2) was 29% (95% CI: 12-42) and 25% (95% CI: -41 to 61), 33% (95% CI: 14-49), and 26% (95% CI: -22 to 55) among those aged 0-14, 15-64, and over 65 years, respectively. The A(H3N2) VE among the influenza vaccination target group was 20% (95% CI: -6 to 39). All 53 sequenced A(H1N1)pdm09 viruses belonged to clade 6B.1A.5a.1. Among 410 sequenced influenza A(H3N2) viruses, all but eight belonged to clade 3C.2a1b.2a.2. DISCUSSION: Despite antigenic mismatch between vaccine and circulating strains for influenza A(H3N2) and A(H1N1)pdm09, 2021-2022 VE estimates against circulating influenza A(H1N1)pdm09 were the highest within the I-MOVE network since the 2009 influenza pandemic. VE against A(H3N2) was lower than A(H1N1)pdm09, but at least one in five individuals vaccinated against influenza were protected against presentation to primary care with laboratory-confirmed influenza.

Surveillance of medically-attended influenza in elderly patients from Romania-data from three consecutive influenza seasons (2015/16, 2016/17, and 2017/18).

BACKGROUND: Influenza is an acute infection affecting all age groups; however, elderly patients are at an increased risk. We aim to describe the clinical characteristics and the circulation of influenza virus types in elderly patients admitted for severe acute respiratory infection (SARI) to a tertiary care hospital in Bucharest, Romania, part of the I-MOVE+ hospital network. METHODS: We conducted an active surveillance study at the National Institute for Infectious Diseases "Prof. Dr Matei Balș," Bucharest, Romania, during three consecutive influenza seasons: 2015/16, 2016/17, and 2017/18. All patients aged 65 and older admitted to our hospital for SARI were tested for influenza by PCR. RESULTS: A total of 349 eligible patients were tested during the study period, and 149 (42.7%) were confirmed with influenza. Most patients, 321 (92.5%) presented at least one underlying condition at the time of hospital admission, the most frequent being cardiovascular disease, 270 (78.3%). The main influenza viral subtype circulating in 2015/16 was A(H1N1)pdm09, followed by A(H3N2) in 2016/17 and B influenza in 2017/18. Case fatality was highest in the 2015/16 season (3.7%), 0% in 2016/17, and 1.0% in 2017/18. Vaccination coverage in elderly patients with SARI from our study population was 22 (6.3%) over the three seasons. CONCLUSIONS: Our study has highlighted a high burden of comorbidities in elderly patients presenting with SARI during winter season in Romania. The influenza vaccine coverage rate needs to be substantially increased in the elderly population, through targeted interventions.

Differentiation of influenza B lineages from clinical samples by one-step real-time RT-PCR.

BACKGROUND: Influenza viruses type A and type B are a leading cause of annual epidemics in human populations. Since the 1970s, influenza B viruses have diverged into two antigenically distinct virus lineages called the Yamagata and Victoria lineages. We describe the validation and implementation of a one-step real-time RT-PCR (rRT-PCR) assay that can differentiate between the two genetic lineages of type B. METHODS: Validation of rRT-PCR method was carried out using quantified positive control and reference influenza viruses with specific minor groove binder (MGB) probes. The assay was applied on 102 clinical specimens detected positive for influenza type B. RESULTS: Detection limit was found to be as low as 7.95 RNA copies per reaction. The interassay variability and intra-assay variability were found to be low, and comparable for Yamagata and Victoria lineages. No cross-reactivity with the tested subtypes of influenza type A, known to cause human infections, was noticed. Differentiation of influenza B lineages by rRT-PCR was successfully achieved on all of the known positive type B samples. From the total number of clinical specimens tested, 85 samples belonged to B/Yamagata and 17 samples to B/Victoria lineage. CONCLUSION: Differentiation of genetic lineage B influenza virus circulating in Romania in the next seasons by one-step real-time RT-PCR method will supplement the classical test, haemagglutination inhibition (HI), which requires growing of the virus. This method can be advantageous for a balanced selection of samples, in case of lineages co-circulation, for genetic and antigenic characterization.

Survival of H5N1 influenza virus in water and its inactivation by chemical methods.

The ability of H5N1 Avian Influenza Virus (AIV) to survive in surface water has been assessed in experimental laboratory conditions, based on non-pathogenic avian reassortant model, by titration of infectivity (TCID50) at different time intervals, in three different types of water. The effect of different chemicals on AIV's survival was assessed using the same type of experimental model. After exposure to the chemical, followed by growth on a suitable substrate, the AIV was quantified by a real-time quantitative reverse transcriptase PCR (qRT-PCR). The reassortant virus persisted, and remained infective in aquatic environments, for 12 days at 22-35 degrees C and up to 20 days at 4 degrees C, irrespective of the type of water, supporting the hypothesis of a potential risk for transmitting the virus among birds and contaminating the household water via common sources of water. A significant decrease for AIV persistence models was recorded for sea water, after 12 days, at 35 degrees C. An effective inactivation has been shown when using commercially available products based on glutaraldehyde and penta potassium bis (peroxy mono sulphate) bis(sulphate), respectively. This rapid and safe method for decontamination, developed in this study, might be helpful in implementation of biosafety measures in laboratory and farms against AIV.

First detection of human metapneumovirus in children with respiratory infections in Romania.

The human metapneumovirus (hMPV) was first isolated in 2001 in the Netherlands (Van der Hoogen and collaborators) from a nasopharyngeal aspirate sampled from an infant. Based on the morphological, biochemical and genetic characteristics, the hMPV was initially classified in the genus Metapneumovirus with the avian metapneumovirus (APV), the agent causing the respiratory infections of the upper tract in turkeys and other birds. Subsequently, together with the respiratory syncytial virus (RSV), it was classified in the Pneumovirus genus which is a part of the Pneumovirinae subfamily, the Paramyxoviridae family. The aim of the present study was to optimize hMPV molecular detection and to detect the virus in samples form children with respiratory infections in Romania. Two types of RTPCR commercial kits were evaluated for the detection of hMPV. Tests were performed on 28 pharyngeal exudates from children aged from 9 months to 6 years, which were negative for influenza viruses and for Respiratory Syncytial Virus (RSV). Among the tested samples 7 (25%) have been positive for hMPV by RT-PCR. These results document for the first time that hMPV is circulating in Romania and causes respiratory infections, especially in newborns and children under 6 years old.