台州市2018/2019年度社区老年人接种流感疫苗的保护效果

目的评估台州市2018/2019年度社区老年人接种三价灭活流感疫苗(TIV)的保护效果(VE)。方法运用前瞻性队列研究设计,招募接种和未接种TIV的≥60岁社区老年人随访6个月,观察流感样疾病(ILI)、因ILI就诊、因ILI或肺炎住院、因呼吸或循环系统疾病住院4种临床结局,计算TIV的VE。结果 TIV接种组、未接种组分别纳入研究对象1 048名、1 025名。接种TIV后1-3月预防4种临床结局的VE(95%CI)分别为-25.1(-80.4-13.2)%、-33.1(-99.2-11.1)%、35.8(-124.9-81.7)%和-12.6(-229.2-61.5)%;接种TIV后4-6月分别为25.5(-7.5-48.4)%、35.1(3.0-56.5)%、1.4(-249.1-72.1)%和-11.5(-240.9-63.5)%;接种TIV后1-6月分别为5.9(-24.2-28.7)%、11.6(-18.9-34.3)%、21.7(-99.2-69.2)%和-13.9(-155.5-49.2)%。结论台州市2018/2019年度社区老年人接种TIV对预防ILI病例发病、就诊和相关住院具有一定的保护效果。     

Negative impact of prior influenza vaccination on current influenza vaccination among people infected and not infected in prior season: A test-negative case-control study in Japan

BackgroundAccumulating evidences indicate that repeated influenza vaccination has negative impact on the vaccine effectiveness (VE). However no published studies considered past influenza infection when assessing the VE of repeated vaccination.MethodsProspective surveillance was conducted from 2009 to 2012 at a community hospital on a small island in Japan. The study included all outpatients with an influenza-like illness (ILI) who attended the hospital, and a rapid diagnostic test (RDT) was used to diagnose influenza A/B infection. The VE of trivalent inactivated influenza vaccine (TIV) against medically attended influenza A (MA-fluA) was estimated using a test-negative case-control study design. The influence of TIV in the prior season on VE in the current season was investigated in the context of MA-fluA during the prior season.ResultsDuring the three influenza seasons, 5838 ILI episodes (4127 subjects) were analysed. Subjects who had an episode of MA-fluA in the prior season were at a significantly lower risk of MA-fluA in the current season (adjusted odds ratio: 0.38, 95% CI: 0.30–0.50). The overall adjusted VE was 28% (95% CI, 14–40). VE was substantially lower in subjects vaccinated in the prior season compared to those who had not been vaccinated in prior season (19%; 95% CI: 0–35 vs 46%; 95% CI: 26–60, test for interaction, P value <0.05). In subjects who did not have MA-fluA in the prior season showed the attenuation of VE due to repeated vaccination (13%; 95% CI: −7 to 30 vs 44%; 95% CI: 24–59, test for interaction, P < 0.05). However this effect was not detected in subjects who had contracted MA-fluA in the prior season.ConclusionsNegative effects of repeated vaccination were significant among those without history of MA-fluA in the prior season.     

No association between 2008-09 influenza vaccine and influenza A(H1N1)pdm09 virus infection, Manitoba, Canada, 2009

We conducted a population-based study in Manitoba, Canada, to investigate whether use of inactivated trivalent influenza vaccine (TIV) during the 2008-09 influenza season was associated with subsequent infection with influenza A(H1N1)pdm09 virus during the first wave of the 2009 pandemic. Data were obtained from a provincewide population-based immunization registry and laboratory-based influenza surveillance system. The test-negative case-control study included 831 case-patients with confirmed influenza A(H1N1)pdm09 virus infection and 2,479 controls, participants with test results negative for influenza A and B viruses. For the association of TIV receipt with influenza A(H1N1)pdm09 virus infection, the fully adjusted odds ratio was 1.0 (95% CI 0.7-1.4). Among case-patients, receipt of 2008-09 TIV was associated with a statistically nonsignificant 49% reduction in risk for hospitalization. In agreement with study findings outside Canada, our study in Manitoba indicates that the 2008-09 TIV neither increased nor decreased the risk for infection with influenza A(H1N1)pdm09 virus.     

Risk of convulsions in children after monovalent H1N1 (2009) and trivalent influenza vaccines: a database study

The monovalent H1N1 (2009) pandemic influenza vaccine used predominantly in the UK in 2009/10 was a split virion vaccine with a novel oil-in-water adjuvant (ASO3). While this was highly immunogenic it was also reactogenic especially for fever in children. There is a paucity of comparative data on reactogenicity of trivalent influenza vaccine (TIV). Using the General Practice Research Database (GPRD) we investigated whether there was an increased risk of convulsions in children vaccinated with monovalent H1N1 influenza vaccine in the 2009/10 season and also the risk after vaccination with the seasonal TIVs using the self-controlled case-series method. A total of 2366 children aged under 10 years with at least one convulsion recorded in the GPRD and who had received at least one influenza vaccine at anytime (2858 doses of TIV and 1895 doses of the monovalent H1N1 influenza vaccine) were identified between May 2000 and April 2010. Over this period these 2366 children had a total of 3846 convulsion episodes. There was no increase in the incidence rate ratio (IRR) in the week after vaccination for either the monovalent H1N1 influenza vaccine (IRR 0.99, 95% CI 0.61-1.60) or the first dose of TIV (IRR 0.89, 95% CI 0.53-1.52). A signal of an elevated risk in the first few days after the second dose of monovalent H1N1 influenza vaccine was seen with an IRR for days 1-3 post vaccination of 3.48 (95% CI 0.86-14.07). This is consistent with findings of increased fever in a clinical trial. These results neither provide evidence of an increased risk of convulsions following TIV over a 10-year surveillance period nor following a single dose of the ASO3 adjuvanted monovalent H1N1 vaccine in 2009/10.     

Influenza vaccine effectiveness against laboratory-confirmed influenza in a vaccine-mismatched influenza B-dominant season

BackgroundThe 2017–2018 influenza season in Israel was characterized by the predominance of influenza B Yamagata, with a lesser circulation of influenza A(H1N1)pdm09 and influenza A(H3N2). We estimated vaccine effectiveness (VE) of the inactivated influenza vaccine which was selected for use that season.MethodsEnd-of-season VE and 95% confidence intervals (CI) against laboratory-confirmed influenza-like illness (ILI) were estimated by means of the test-negative design. Age-specific VE analysis was carried out using a moving age interval.ResultsSpecimen were obtained from 1,453 community ILI patients; 610 (42.0%) were influenza-positive, among which 69.7% were B, 17.2% A(H1N1)pdm09 and 13.4% A(H3N2). A 98.6% of molecularly characterized influenza B belonged to the Yamagata lineage. Of the sampled individuals, 1320 were suitable for VE analysis. Of those vaccinated, 90.6% received the inactivated trivalent influenza vaccine (TIV) containing a Victoria lineage influenza B-like virus. VE against influenza A differed by age, with the highest VE of 72.9% (95%CI 31.9–89.2%) observed in children 0.5–14 years old, while all ages VE was 46.6% (95%CI 10.4–68.2%). All ages VE against influenza B was 23.2% (95%CI −10.1–46.4%) with age-specific analysis showing non-significant VE estimates. Utilizing a moving age interval of 15 years, afforded a detailed age-specific insight into influenza VE against the influenza viruses circulating during the 2017–2018 season.ConclusionsThe moderate-high 2017–2018 influenza A VE among children and adolescents, supports seasonal influenza vaccination at a young age. The low VE against influenza B in Israel, is most likely the result of influenza B/TIV-mismatch.     

The effectiveness of trivalent inactivated influenza vaccine in children over six consecutive influenza seasons

Objective

To estimate the effectiveness of two doses of trivalent inactivated influenza vaccine (TIV) over six consecutive influenza seasons in a small community in Japan.

Patients and methods

A prospective, non-randomized, observational study of TIV effectiveness was performed involving children aged 6 months to 6 years accessing pediatric services in Soma and Shinchi, Japan. The total number of children under observation was 14,788. Each fall from 2002 to 2007 TIV was offered to all children with an average uptake of 52.9%. Influenza rapid diagnostic tests were performed to all children with respiratory symptoms and a temperature >38 °C during each surveillance period. The efficacy of two doses of TIV was estimated by the relative risk of influenza illness and influenza associated hospitalizations and effectiveness by reduction in all respiratory illness in vaccinated and unvaccinated children.

Results

Influenza A occurred each year resulting in approximately one in five children in the unvaccinated group having an influenza A related clinic visit. For influenza A, two doses of TIV showed yearly efficacies that ranged from 42% to 69% with the highest efficacy during the 2002/2003 influenza season when the vaccine strains were well matched with the circulating viruses. The overall efficacy of two doses of TIV against influenza A and B associated illness was 52% and 59%, respectively. TIV also reduced the rate of the influenza associated hospitalizations attributable to both influenza A and B.

Conclusions

Vaccination with two doses of TIV was consistently effective in preventing influenza-associated clinic visits and hospitalizations.     

Estimates of influenza vaccine effectiveness in primary care in Scotland vary with clinical or laboratory endpoint and method—Experience across the 2010/11 season

Aim

This study examines estimation of seasonal influenza vaccine effectiveness (VE) for a cohort of patients attending general practice in Scotland in 2010/11. The study focuses on the variation in estimation of VE for both virological and clinical consultation outcomes and understanding the dependency on date of analysis during the season, methodological approach and the effect of use of a propensity score model.

Methods

For the clinical outcomes, three methodological approaches were considered; adjusted Poisson multi-level modelling splitting consultations in vaccinated individuals into those before and after vaccination, adjusted Cox proportional hazards modelling and finally the screening method. For the virological outcome, the test-negative case–control study design was employed.

Results

VE was highest for the most specific outcomes of ILI (Poisson end-of-season VE = 47% (95% CI: −69%, 83%); Cox VE = 34% (95% CI: −64%, 73.2%); Screening VE = 52.8% (95% CI: 3.8%, 76.8%)) and a virological diagnosis (VE = 54% (95% CI: −37%, 85%)). Using the Cox approach, adjusted for propensity score only gave VE = 46.5% (95% CI: −30.4%, 78.0%).

Conclusion

Our approach illustrated the ability to achieve relatively consistent estimates of seasonal influenza VE using both specific and less specific outcomes. Construction of a propensity score and use for bias adjustment increased the estimate of ILI VE estimated from the Cox model and made estimates more similar to the Poisson approach, which models differences in consultation behaviour of vaccinated individuals more inherently in its structure. VE estimation for the same data was found to vary by methodology which should be noted when comparing results from different studies and countries.     

Lineage-matched versus mismatched influenza B vaccine effectiveness following seasons of marginal influenza B circulation

BackgroundSeveral countries have recently transitioned from the trivalent inactivated influenza vaccine (TIV) to the quadrivalent inactivated influenza vaccine (QIV) in order to outweigh influenza B vaccine-mismatch. However, few studies thus far evaluated its benefits versus the TIV in a systematic manner. Our objective was to compare the QIV VE with lineage-mismatched TIV VE.MethodsWe estimated the 2015–2016, 2017–2018, 2019–2020 end-of season influenza B VE against laboratory-confirmed influenza-like illness (ILI) among community patients, using the test-negative design. VE was estimated for pre-determined age groups and for moving age intervals of 15 years.ResultsSince 2011–2012 season, alternate seasons in Israel were dominated by influenza B circulation. Compared with the lineage-mismatched TIV used during the 2015–2016 and 2017–2018 seasons, the 2019–2020 QIV showed the highest all-ages VE, with VE estimates of 56.9 (95% CI 30.1 to 73.4), 16.5 (95% CI –22.5 to 43.1) and ?25.8 (95% CI ?85.3 to 14.6) for the 2019–2020, 2017–2018 and 2015–2016 seasons, respectively. The 2019–2020 VE point estimated were the highest for the 0.5–4, 5–17 and 18–44 years age groups and for more 15-year age intervals as compared to the other seasons.ConclusionsOur results support the rapid transition from the TIV to the QIV.     

Influenza pandemic (H1N1) 2009 activity during summer 2009. Effectiveness of the 2008-9 trivalent vaccine against pandemic influenza in Spain

Introduction

The Spanish influenza surveillance system (SISS) maintained its activity during the summer of 2009 to monitor the influenza pandemic.

Objectives

To describe pandemic influenza activity from May to September 2009 and to estimate the effectiveness of the 2008-9 seasonal influenza vaccine against laboratory-confirmed pandemic (H1N1) 2009 influenza.

Methods

Data from the SISS were used to identify the trend of pandemic (H1N1) 2009 influenza outside the influenza season. For the effectiveness study, we compared the vaccination status of notified cases [influenza-like illnesses (ILI) laboratory confirmed as pandemic influenza] with that of the test-negative controls.

Results

The first laboratory-confirmed case of the pandemic virus was notified in the system in week 20/2009. The ILI rate increased gradually in the study period, exceeding basic activity in week 38. The proportion of pandemic (H1N1) 2009 influenza viruses detected by the system represented 14% in week 20/2009 and rapidly increased to 90% in week 34. The adjusted vaccine effectiveness of the 2008-9 seasonal vaccine against laboratory-confirmed pandemic influenza was 12% (-30; 41).

Conclusions

The SISS became an essential tool for pandemic monitoring in Spain. The improved SISS will provide more accurate information on influenza activity in future seasonal or pandemic waves. Using surveillance data, we could not demonstrate the effectiveness of the seasonal 2008-9 vaccine against laboratory-confirmed pandemic influenza.     

Inactivated influenza vaccine effectiveness and an analysis of repeated vaccination for children during the 2016/17 season

ObjectivesWe assessed the vaccine effectiveness (VE) of inactivated influenza vaccine (IIV) in children 6 months to 15 years of age during the 2016/17 season. In addition, we estimated the impact of repeated vaccination in children on VE.MethodsOur study for VEs in preventing influenza and admission due to influenza were conducted according to a test-negative case-control design (TNCC) based on influenza rapid diagnostic test results. We also analyzed the VE by vaccine status in the current and previous seasons for the impact of repeated vaccination.ResultsDuring the 2016/17 season, the quadrivalent IIV was used in Japan. The adjusted VE in preventing influenza illness was 38% (95% CI, 29–46) against influenza A and 39% (95% CI, 18–54) against influenza B. Infants showed no significant VE. The VE in preventing hospitalization was not demonstrated. For the analysis of repeated vaccination, the vaccine was effective only when immunization occurred in the current season. The children who were immunized in two consecutive seasons were more likely to develop influenza compared to those immunized in the current season only (odds ratio, 1.58 [95% CI, 1.05–2.38], adjusted odds ratio, 1.53 [95% CI, 0.99–2.35]). However, the odds ratio of repeated vaccination was not significant when the analysis excluded those who developed influenza in the previous season.ConclusionsVE in children in the 2016/17 season was similar to values previously reported. Repeated vaccination interfered with the VE against any influenza infection in the 2016/17 season. The results of our study suggest that decreased VE by repeat vaccination phenomenon was associated with immunity by influenza infection in the previous season. However, the influenza vaccine should be recommended every season for children.     

Evaluation of the Effectiveness of Pandemic Influenza A(H1N1) 2009 Vaccine Based on an Outbreak Investigation During the 2010–2011 Season in Korean Military Camps

Objectives

In December 2010, there was an outbreak of acute febrile respiratory disease in many Korean military camps that were not geographically related. A laboratory analysis confirmed a number of these cases to be infected by the pandemic influenza A(H1N1) 2009 (H1N1pdm09) virus. Because mass vaccination against H1N1pdm09 was implemented at the infected military camps eleven months ago, the outbreak areas in which both vaccinated and nonvaccinated individuals were well mixed, gave us an opportunity to evaluate the effectiveness of H1N1pdm09 vaccine through a retrospective cohort study design.

Methods

A self-administered questionnaire was distributed to the three military camps in which the outbreak occurred for case detection, determination of vaccination status, and characterization of other risk factors. The overall response rate was 86.8% (395/455). Case was defined as fever (≥38 °C) with cough or sore throat, influenza-like illness (ILI), and vaccination status verified by vaccination registry. Crude vaccine effectiveness (VE) was calculated as “1 − attack rate in vaccinated individuals/attack rate in nonvaccinated individuals”, and adjusted VE was calculated as “1 – odds ratio” using logistic regression adjusted for potential confounding factor. A number of ILI definitions were used to test the robustness of the result.

Results

The attack rate of ILI was 12.8% in register-verified vaccinated individuals and 24.0% in nonvaccinated individuals. The crude VE was thus calculated to be 46.8% [95% confidence interval (CI): 14.5–66.9]. The adjusted VE rate was 46.8% (95% CI: –9.4 to 74.1). Various combinations of ILI symptoms also showed similar VE rates.

Conclusion

We evaluated the effectiveness of H1N1pdm09 vaccine in the 2010–2011 season in an outbreak setting. Although the result was not sensitive to any analytical method used and ILI case definition, the magnitude of effectiveness was lower than estimated in the 2009–2010 season.     

Frailty is associated with impairment of vaccine-induced antibody response and increase in post-vaccination influenza infection in community-dwelling older adults

Annual immunization with a trivalent inactivated vaccine (TIV) is considered efficacious for prevention of seasonal influenza in older adults. However, significant controversy exists in the current literature regarding the clinical effectiveness of TIV immunization in this highly heterogeneous population. Frailty is an important geriatric syndrome characterized by decreased physiologic reserve and increased vulnerability to stressors. Using a validated set of frailty criteria, we conducted a prospective observational study to evaluate TIV-induced strain-specific hemagglutination inhibition (HI) antibody titers and post-vaccination rates of influenza-like illness (ILI) and infection in frail and nonfrail older adults. The results indicate that frailty was associated with significant impairment in TIV-induced strain-specific HI titers and increased rates of ILI and laboratory-confirmed influenza infection. These findings suggest that assessing frailty status in the elderly may identify those who are less likely to respond to TIV immunization and be at higher risk for seasonal influenza and its complications.     

Impacts on influenza A(H1N1)pdm09 infection from cross-protection of seasonal trivalent influenza vaccines and A(H1N1)pdm09 vaccines: systematic review and meta-analyses

Cross-protection by seasonal trivalent influenza vaccines (TIVs) against pandemic influenza A H1N1 2009 (now known as A[H1N1]pdm09) infection is controversial; and the vaccine effectiveness (VE) of A(H1N1)pdm09 vaccines has important health-policy implications. Systematic reviews and meta-analyses are needed to assess the impacts of both seasonal TIVs and A(H1N1)pdm09 vaccines against A(H1N1)pdm09.We did a systematic literature search to identify observational and/or interventional studies reporting cross-protection of TIV and A(H1N1)pdm09 VE from when the pandemic started (2009) until July 2011. The studies fulfilling inclusion criteria were meta-analysed. For cross-protection and VE, respectively, we stratified by vaccine type, study design and endpoint. Seventeen studies (104,781 subjects) and 10 studies (2,906,860 subjects), respectively, reported cross-protection of seasonal TIV and VE of A(H1N1)pdm09 vaccines; six studies (17,229 subjects) reported on both. Thirteen studies (95,903 subjects) of cross-protection, eight studies (859,461 subjects) of VE, and five studies (9,643 subjects) of both were meta-analysed and revealed: (1) cross-protection for confirmed illness was 19% (95% confident interval=13-42%) based on 13 case-control studies with notable heterogeneity. A higher cross-protection of 34% (9-52%) was found in sensitivity analysis (excluding five studies with moderate/high risk of bias). Further exclusion of studies that recruited early in the pandemic (when non-recipients of TIV were more likely to have had non-pandemic influenza infection that may have been cross-protective) dramatically reduced heterogeneity. One RCT reported cross-protection of 38% (19-53%) for confirmed illness. One case-control study reported cross-protection of 50% (40-59%) against hospitalisation. (2) VE of A(H1N1)pdm09 for confirmed illness was 86% (73-93%) based on 11 case-control studies and 79% (22-94%) based on two cohort studies; VE against medically-attended ILI was 32% (8-50%) in one cohort study. TIVs provided moderate cross-protection against both laboratory-confirmed A(H1N1)pdm09 illness (based on eight case-control studies with low risk of bias and one RCT) and also hospitalisation. A finding of increased risk from seasonal vaccine was limited to cases recruited early in the pandemic. A(H1N1)pdm09 vaccines were highly effective against confirmed A(H1N1)pdm09 illness. Although cross-protection was less than the direct effect of strain-specific vaccination against A(H1N1)pdm09, TIV was generally beneficial before A(H1N1)pdm09 vaccine was available.     

Estimates of 2012/13 influenza vaccine effectiveness using the case test-negative control design with different influenza negative control groups

Background

In recent years several reports of influenza vaccine effectiveness (VE) have been made early for public health decision. The majority of these studies use the case test-negative control design (TND), which has been showed to provide, under certain conditions, unbiased estimates of influenza VE. Nevertheless, discussions have been taken on the best influenza negative control group to use. The present study aims to contribute to the knowledge on this field by comparing influenza VE estimates using three test-negative controls: all influenza negative, non-influenza respiratory virus and pan-negative.

Methods

Incident ILI patients were prospectively selected and swabbed by a sample of general practitioners. Cases were ILI patients tested positive for influenza and controls ILI patients tested negative for influenza. The influenza negative control group was divided into non-influenza virus control group and pan-negative control group. Data were collected on vaccination status and confounding factors. Influenza VE was estimated as one minus the odds ratio of been vaccinated in cases versus controls adjusted for confounding effect by logistic regression.

Results

Confounder adjusted influenza VE against medically attended laboratory-confirmed influenza was 68.4% (95% CI: 20.7–87.4%) using all influenza negatives controls, 82.1% (95% CI: 47.6–93.9%) using non-influenza controls and 49.4% (95% CI: −44.7% to 82.3%) using pan-negative controls.

Conclusions

Influenza VE estimates differed according to the influenza negative control group used. These results are in accordance with the expected under the hypothesis of differential viral interference between influenza vaccinated and unvaccinated individuals. Given the wide importance of TND study further studies should be conducted in order to clarify the observed differences.     

The effect of seasonal influenza vaccine on medically-attended influenza and non-influenza respiratory viruses infections at primary care level,Hong Kong SAR, 2017/18 to 2019/20

Effectiveness of seasonal influenza vaccine (SIV) varies with the degree of matching with the vaccine and circulating viruses. We continued our SIV effectiveness against medically-attended influenza-like illness (ILI) under the Department of Health Hong Kong’s sentinel private medical practitioners (PMP) network, using the test-negative case-control design, for the 2018/19 and 2019/20 season. In addition, we studied the potential interference between SIV and ILI caused by non-influenza respiratory viruses (NIRV) based on data collated from 2017/18 to 2019/20 seasons. 3404 patients were analysed. Across the 2017/18 to 2019/20 seasons, the vaccine effectiveness (VE) of SIV was 44% (95% CI 30–56%) against pan-negative controls, 57% (95%CI. 42–68%) against NIRV controls and 50% (95%CI 38–59%) against both. SIV was moderately effective against medically-attended ILI caused by influenza A/B in both 2018/19 and 2019/20 winter seasons (53.2% (95%CI 36.7–65.5%) and 41.8% (95%CI 6.3–64.1%), respectively). The VE against the main circulating subtype, influenza A(H1), was higher for the 2018/19 season (57.2% (95%CI 39.8–69.9%), compared to 34.6% (95%CI −9.6–61.4%) in the 2019/20 season). When compared to pan negative controls, those with single NIRV infections were similarly likely to have received SIV (OR 1.05 (95%CI 0.72–1.54) within the influenza season; OR 0.97 (95%CI 0.73–1.29) when including non-influenza seasons). Analyses by type of virus showed no increased risk of SIV identified among those with single infections of EV/RV, HMPV and parainfluenza but a 2-fold increased risk was shown for those with single infections of adenovirus and parainfluenza virus (adenovirus: OR 2.54 (95%CI 1.24–5.14) within influenza season and OR 1.78 (95%CI 1.01–3.09) for the whole period; parainfluenza virus: OR 2.01 (95%CI 1.22–3.29) within influenza season and OR 1.89 (95%CI 1.29–2.76) for the whole period). SIV programme and surveillance of influenza and NIRV, including SARS-CoV-2, should continue during the COVID-19 pandemic.     

Consultations for Influenza-Like Illness in Primary Care in The Netherlands: A Regression Approach

ObjectivesTo estimate the general practitioner (GP) consultation rate attributable to influenza in The Netherlands.MethodsRegression analysis was performed on the weekly numbers of influenza-like illness (ILI) GP consultations and laboratory reports for influenza virus types A and B and 8 other pathogens over the period 2003–2014 (11 influenza seasons; week 40–20 of the following year).ResultsIn an average influenza season, 27% and 11% of ILI GP consultations were attributed to infection by influenza virus types A and B, respectively. Influenza is therefore responsible for approximately 107 000 GP consultations (651/100 000) each year in The Netherlands. GP consultation rates associated with influenza infection were highest in children under 5 years of age, at 667 of 100 000 for influenza A and 258 of 100 000 for influenza B. Influenza virus infection was found to be the predominant cause of ILI-related GP visits in all age groups except children under 5, in which respiratory syncytial virus (RSV) infection was found to be the main contributor.ConclusionsThe burden of influenza in terms of GP consultations is considerable. Overall, influenza is the main contributor to ILI. Although ILI symptoms in children under 5 years of age are most often associated with RSV infection, the majority of visits related to influenza occur among children under 5 years of age.     

Influenza vaccine effectiveness to prevent influenza-related hospitalizations and serious outcomes in Canadian adults over the 2011/12 through 2013/14 influenza seasons: A pooled analysis from the Canadian Immunization Research Network (CIRN) Serious Outcomes Surveillance (SOS Network)

BackgroundOngoing assessment of influenza vaccine effectiveness (VE) is critical to inform public health policy. This study aimed to determine the VE of trivalent influenza vaccine (TIV) for preventing influenza-related hospitalizations and other serious outcomes over three consecutive influenza seasons.MethodsThe Serious Outcomes Surveillance (SOS) Network of the Canadian Immunization Research Network (CIRN) conducted active surveillance for influenza in adults ≥16 years (y) of age during the 2011/2012, 2012/2013 and 2013/2014 seasons in hospitals across Canada. A test-negative design was employed: cases were polymerase chain reaction (PCR)-positive for influenza; controls were PCR-negative for influenza and were matched to cases by date, admission site, and age (≥65 y or <65 y). All cases and controls had demographic and clinical characteristics (including influenza immunization status) obtained from the medical record. VE was estimated as 1-OR (odds ratio) in vaccinated vs. unvaccinated patients × 100%. The primary outcome was VE of TIV for preventing laboratory-confirmed influenza-related hospitalization; secondary outcomes included VE of TIV for preventing influenza-related intensive care unit (ICU) admission/mechanical ventilation, and influenza-related death.ResultsOverall, 3394 cases and 4560 controls were enrolled; 2078 (61.2%) cases and 2939 (64.5%) controls were ≥65 y. Overall matched, adjusted VE was 41.7% (95% Confidence Interval (CI): 34.4–48.3%); corresponding VE in adults ≥65 y was 39.3% (95% CI: 29.4–47.8%) and 48.0% (95% CI: 37.5–56.7%) in adults <65 y, respectively. VE for preventing influenza-related ICU admission/mechanical ventilation in all ages was 54.1% (95% CI: 39.8–65.0%); in adults ≥65 y, VE for preventing influenza-related death was 74.5% (95% CI: 44.0–88.4%).ConclusionsWhile effectiveness of TIV to prevent serious outcomes varies year to year, we demonstrate a statistically significant and clinically important TIV VE for preventing hospitalization and other serious outcomes over three seasons. Public health messaging should highlight the overall benefit of influenza vaccines over time while acknowledging year to year variability.ClinicalTrials.gov Identifier: NCT01517191.     

A retrospective survey of the safety of trivalent influenza vaccine among adults working in healthcare settings in south metropolitan Perth, Western Australia, in 2010

In Australia, annual vaccination with trivalent influenza vaccine (TIV) is recommended for healthcare providers. Each year, an influenza vaccination program is run in south metropolitan area hospitals in Perth, Western Australia. In 2010, a survey to examine side effects following vaccination and subsequent significant respiratory illnesses during the influenza season was undertaken. A total of 2245 individuals vaccinated in the area-wide hospital vaccination program responded, representing 50% of consenting recipients. Data linkage was performed to ascertain additional information such as brand details. Side effects within 48 h of receipt of the influenza vaccine were reported by 387 (17.2%). Only 30 respondents (1.3%) had to seek health advice following a side effect temporally related to influenza vaccination and 10 (0.4%) required treatment. Recipients who received Fluvax^® (364, 18.0%; CSL Biotherapies) were more likely to report side effects than those who received another brand (23, 10.2%; OR 1.94, 95% CI 1.24–3.03, P = 0.004). The difference in the side effect profiles was largely confined to systemic effects. Most respondents (1621, 72.2%) did not require time off work for a respiratory illness during the subsequent influenza season. Overall, the influenza vaccine was demonstrated to be safe among this large sample of predominantly healthcare workers. A higher rate of adverse events, albeit primarily mild, was reported among recipients of Fluvax^® in 2010.     

A postmarketing evaluation of the frequency of use and safety of live attenuated influenza vaccine use in nonrecommended children younger than 5 years

The 2007 US approval for use of live attenuated influenza vaccine (LAIV) in children aged 24-59 months included precautions against use in (1) children <24 months and children aged 24-59 months with (2) asthma, (3) recurrent wheezing, and (4) altered immunocompetence. A postmarketing commitment was initiated to monitor LAIV use and the frequency of select safety outcomes in these cohorts. Vaccination rates and the frequency of hospitalizations or emergency department visits within 42 days after LAIV and trivalent inactivated influenza vaccine (TIV) administration were estimated from 2007 to 2009 claims data from a health insurance database. Rates of LAIV use per 10,000 child-days among cohorts 1, 2, and 4 were low relative to rates among the LAIV-recommended population (2007-2008; 0.03-0.78 vs. 1.32, 2008-2009; 0.08-3.26 vs. 5.94). However, rates of LAIV use per 10,000 child-days in cohort 3 were similar to rates among the LAIV-recommended population (2007-2008; 1.55 vs. 1.32, 2008-2009; 5.01 vs. 5.94). The rate of emergency department visits/hospitalizations within 42 days of vaccination with LAIV was the same as or less than the rate within 42 days of vaccination with TIV. Less restricted LAIV use in children with past wheezing may be related to the broad definition of recurrent wheezing used in national guidelines and the current study. In the small number of nonrecommended children receiving LAIV, no safety signals were identified.     

Effectiveness of the 2011–12 Influenza Vaccine: Data from US Military Dependents and US-Mexico Border Civilians

Objective

To assess effectiveness of the influenza vaccine among US military dependents and US-Mexico Border populations during the 2011–12 influenza season.

Introduction

As a result of antigenic drift of the influenza viruses, the composition of the influenza vaccine is updated yearly to match circulating strains. Consequently, there is need to assess the effectiveness of the influenza vaccine (VE) on a yearly basis. Ongoing febrile respiratory illness (FRI) surveillance captures data and specimens that are leveraged to estimate influenza VE on an annual basis.

Methods

Data from ongoing FRI surveillance at US Military and US-Mexico border clinics were used to estimate VE. We conducted a case–control study between weeks 3 and 17 of the 2011–12 influenza season. Specimens were collected from individuals meeting FRI case definition (fever ≥ 100.0 F with either cough or sore throat). Cases were laboratory confirmed influenza infection and controls were negative for influenza. Interviewer-administered questionnaires collected information on patient demographics and clinical factors and vaccination status. Logistic regression was used to calculate the crude and adjusted odds ratios (OR) and VE was computed as (1-OR) × 100%. Vaccine protection was assumed to begin 14 days post-vaccination.

Results

A total of 155 influenza positive cases and 429 influenza negative controls were included in the analysis - 72 cases were influenza A(H3N2), 38 cases were influenza A(H1N1), and 45 cases were influenza B. Overall adjusted VE against laboratory-confirmed influenza was 46% (95% CI, 19–64%); unadjusted was 39% (95% CI, 11–58%). Influenza subtype analyses revealed moderate protection against A/H3 and A/H1 and lower protection against B. Lowest estimated VE was seen in older individuals, age 65 and older.

Conclusions

Influenza vaccination was moderately protective against laboratory confirmed influenza in this population. Continued surveillance is important in monitoring the effectiveness of the influenza vaccine.