Influenza vaccine effectiveness in patients hospitalized with severe acute respiratory infection in Lithuania during the 2019-2020 influenza season: a test negative case - control study.

BACKGROUND: Influenza is a contagious viral airborne disease that adds to the clinical and economic burden on the healthcare system. It could be prevented substantially by seasonal influenza vaccination. Seasonal influenza vaccine effectiveness (SIVE) varies a lot and should therefore be monitored. This report aims to update age-stratified SIVE estimates among patients hospitalized due to severe acute respiratory infection (SARI) during the 2019-2020 influenza season. METHODS: We performed a test-negative case-control study between December 2019 and April 2020 influenza season. We estimated SIVE and its 95% confidence intervals (95% CI) with logistic regression as (1-odds ratio)*100%. The models were adjusted for covariates that changed the unadjusted SIVE by ≥ 10%. RESULTS: Among 84 participants, 32 (38.1%) were influenza positive, mostly with A(H1N1)pdm09 (25 cases; 78.1%). SIVE against any influenza adjusted for age and heart disease was 39.2% (95% CI: -119.3%, 83.1%). Age-stratified point estimates adjusted for heart diseases indicated different SIVE, and were 64.0% (95% CI: -309.2%, 96.8%) and 21.6% (95% CI: -252.2%, 82.6%) for 18-64 and ≥ 65 year-old participants, respectively. CONCLUSIONS: The point estimates suggested low to moderate SIVE against any influenza among hospitalized 18-64-year-old SARI participants, while low estimates were found in the ≥ 65-year-old group. Although broad SIVE confidence intervals indicate a small sample size and therefore the results can serve only as indicatory, they are in line with the estimates reported by other studies during the 2019-2020 season.

Vaccine effectiveness against COVID-19 hospitalisation in adults (≥ 20 years) during Alpha- and Delta-dominant circulation: I-MOVE-COVID-19 and VEBIS SARI VE networks, Europe, 2021.

IntroductionTwo large multicentre European hospital networks have estimated vaccine effectiveness (VE) against COVID-19 since 2021.AimWe aimed to measure VE against PCR-confirmed SARS-CoV-2 in hospitalised severe acute respiratory illness (SARI) patients ≥ 20 years, combining data from these networks during Alpha (March-June)- and Delta (June-December)-dominant periods, 2021.MethodsForty-six participating hospitals across 14 countries follow a similar generic protocol using the test-negative case-control design. We defined complete primary series vaccination (PSV) as two doses of a two-dose or one of a single-dose vaccine ≥ 14 days before onset.ResultsWe included 1,087 cases (538 controls) and 1,669 cases (1,442 controls) in the Alpha- and Delta-dominant periods, respectively. During the Alpha period, VE against hospitalisation with SARS-CoV2 for complete Comirnaty PSV was 85% (95% CI: 69-92) overall and 75% (95% CI: 42-90) in those aged ≥ 80 years. During the Delta period, among SARI patients ≥ 20 years with symptom onset ≥ 150 days from last PSV dose, VE for complete Comirnaty PSV was 54% (95% CI: 18-74). Among those receiving Comirnaty PSV and mRNA booster (any product) ≥ 150 days after last PSV dose, VE was 91% (95% CI: 57-98). In time-since-vaccination analysis, complete all-product PSV VE was > 90% in those with their last dose < 90 days before onset; ≥ 70% in those 90-179 days before onset.ConclusionsOur results from this EU multi-country hospital setting showed that VE for complete PSV alone was higher in the Alpha- than the Delta-dominant period, and addition of a first booster dose during the latter period increased VE to over 90%.

Vaccine effectiveness against COVID-19 hospitalisation in adults (≥ 20 years) during Omicron-dominant circulation: I-MOVE-COVID-19 and VEBIS SARI VE networks, Europe, 2021 to 2022.

IntroductionThe I-MOVE-COVID-19 and VEBIS hospital networks have been measuring COVID-19 vaccine effectiveness (VE) in participating European countries since early 2021.AimWe aimed to measure VE against PCR-confirmed SARS-CoV-2 in patients ≥ 20 years hospitalised with severe acute respiratory infection (SARI) from December 2021 to July 2022 (Omicron-dominant period).MethodsIn both networks, 46 hospitals (13 countries) follow a similar test-negative case-control protocol. We defined complete primary series vaccination (PSV) and first booster dose vaccination as last dose of either vaccine received ≥ 14 days before symptom onset (stratifying first booster into received < 150 and ≥ 150 days after last PSV dose). We measured VE overall, by vaccine category/product, age group and time since first mRNA booster dose, adjusting by site as a fixed effect, and by swab date, age, sex, and presence/absence of at least one commonly collected chronic condition.ResultsWe included 2,779 cases and 2,362 controls. The VE of all vaccine products combined against hospitalisation for laboratory-confirmed SARS-CoV-2 was 43% (95% CI: 29-54) for complete PSV (with last dose received ≥ 150 days before onset), while it was 59% (95% CI: 51-66) after addition of one booster dose. The VE was 85% (95% CI: 78-89), 70% (95% CI: 61-77) and 36% (95% CI: 17-51) for those with onset 14-59 days, 60-119 days and 120-179 days after booster vaccination, respectively.ConclusionsOur results suggest that, during the Omicron period, observed VE against SARI hospitalisation improved with first mRNA booster dose, particularly for those having symptom onset < 120 days after first booster dose.

Vaccine effectiveness against influenza hospitalisation in adults during the 2022/2023 mixed season of influenza A(H1N1)pdm09, A(H3N2) and B circulation, Europe: VEBIS SARI VE hospital network.

We conducted a multicentre hospital-based test-negative case-control study to measure vaccine effectiveness (VE) against PCR-confirmed influenza in adult patients with severe acute respiratory infection (SARI) during the 2022/2023 influenza season in Europe. Among 5547 SARI patients ≥18 years, 2963 (53%) were vaccinated against influenza. Overall VE against influenza A(H1N1)pdm09 was 11% (95% CI: -23-36); 20% (95% CI: -4-39) against A(H3N2) and 56% (95% CI: 22-75) against B. During the 2022/2023 season, while VE against hospitalisation with influenza B was >55%, it was ≤20% for influenza A subtypes. While influenza vaccination should be a priority for future seasons, improved vaccines against influenza are needed.