The Impact of Prior Season Vaccination on Subsequent Influenza Vaccine Effectiveness to Prevent Influenza-related Hospitalizations Over 4 Influenza Seasons in Canada

2018 ◽  
Vol 69 (6) ◽  
pp. 970-979 ◽  
Author(s):  
M K Nichols ◽  
M K Andrew ◽  
L Ye ◽  
T F Hatchette ◽  
A Ambrose ◽  
...  
Keyword(s):  
Influenza Vaccine ◽  
Negative Impact ◽  
Conditional Logistic Regression ◽  
Vaccine Effectiveness ◽  
Influenza B ◽  
Current Season ◽  
Vaccination Recommendations ◽  
Vaccine Impact ◽  
H3n2 Influenza ◽  
The Impact

Abstract Background Recent studies have demonstrated the possibility of negative associations between prior influenza vaccines and subsequent influenza vaccine effectiveness (VE), depending on season and strain. We investigated this association over 4 consecutive influenza seasons (2011–2012 through 2014–2015) in Canada. Methods Using a matched test-negative design, laboratory-confirmed influenza cases and matched test-negative controls admitted to hospitals were enrolled. Patients were stratified into 4 groups according to influenza vaccine history (not vaccinated current and prior season [referent], vaccinated prior season only, vaccinated current season only, and vaccinated both current and prior season). Conditional logistic regression was used to estimate VE; prior vaccine impact was assessed each season for overall effect and effect stratified by age (<65 years, ≥65 years) and type/subtype (A/H1N1, A/H3N2, influenza B). Results Overall, mainly nonsignificant associations were observed. Trends of nonsignificant decreased VE among patients repeatedly vaccinated in both prior and current season relative to the current season only were observed in the A/H3N2-dominant seasons of 2012–2013 and 2014–2015. Conversely, in 2011–2012, during which B viruses circulated, and in 2013–2014, when A/H1N1 circulated, being vaccinated in both seasons tended to result in a high VE in the current season against the dominant circulating subtype. Conclusions Prior vaccine impact on subsequent VE among Canadian inpatients was mainly nonsignificant. Even in circumstances where we observed a trend of negative impact, being repeatedly vaccinated was still more effective than not receiving the current season’s vaccine. These findings favor continuation of annual influenza vaccination recommendations, particularly in older adults. Clinical Trials Registration NCT01517191.

scholarly journals Influenza vaccine effectiveness against laboratory-confirmed influenza in hospitalised adults aged 60 years or older, Valencia Region, Spain, 2017/18 influenza season

2019 ◽  
Vol 24 (31) ◽  
Author(s):  
Ainara Mira-Iglesias ◽  
F Xavier López-Labrador ◽  
Víctor Baselga-Moreno ◽  
Miguel Tortajada-Girbés ◽  
Juan Mollar-Maseres ◽  
...  
Keyword(s):  
Influenza Vaccine ◽  
Influenza A ◽  
Vaccine Effectiveness ◽  
Influenza Viruses ◽  
Influenza B ◽  
Current Season ◽  
Hospitalised Patients ◽  
Influenza A H1n1 ◽  
Vaccine Type ◽  
The Impact

Introduction Influenza immunisation is recommended for elderly people each season. The influenza vaccine effectiveness (IVE) varies annually due to influenza viruses evolving and the vaccine composition. Aim To estimate, in inpatients ≥ 60 years old, the 2017/18 trivalent IVE, overall, by vaccine type and by strain. The impact of vaccination in any of the two previous seasons (2016/17 and 2015/16) on current (2017/18) IVE was also explored. Methods This was a multicentre prospective observational study within the Valencia Hospital Surveillance Network for the Study of Influenza and Respiratory Viruses Disease (VAHNSI, Spain). The test-negative design was applied taking laboratory-confirmed influenza as outcome and vaccination status as main exposure. Information about potential confounders was obtained from clinical registries and/or by interviewing patients; vaccine information was only ascertained by registries. Results Overall, 2017/18 IVE was 9.9% (95% CI: −15.5 to 29.6%), and specifically, 48.3% (95% CI: 13.5% to 69.1%), −29.9% (95% CI: −79.1% to 5.8%) and 25.7% (95% CI: −8.8% to 49.3%) against A(H1N1)pdm09, A(H3N2) and B/Yamagata lineage, respectively. For the adjuvanted and non-adjuvanted vaccines, overall IVE was 10.0% (95% CI: −24.4% to 34.9%) and 7.8% (95% CI: −23.1% to 31.0%) respectively. Prior vaccination significantly protected against influenza B/Yamagata lineage (IVE: 50.2%; 95% CI: 2.3% to 74.6%) in patients not vaccinated in the current season. For those repeatedly vaccinated against influenza A(H1N1)pdm09, IVE was 46.4% (95% CI: 6.8% to 69.2%). Conclusion Our data revealed low vaccine effectiveness against influenza in hospitalised patients ≥60 years old in 2017/18. Prior vaccination protected against influenza A(H1N1)pdm09 and B/Yamagata-lineage.

scholarly journals Vaccine effectiveness against influenza-associated hospitalization among children aged < 13 years using a hospital-based surveillance system in Minnesota, 2013 – 2016

2017 ◽  
Vol 4 (suppl_1) ◽  
pp. S60-S60
Author(s):  
Ashley Fowlkes ◽  
Hannah Friedlander ◽  
Andrea Steffens ◽  
Kathryn Como-Sabetti ◽  
Dave Boxrud ◽  
...  
Keyword(s):  
Influenza Vaccine ◽  
Influenza Vaccination ◽  
Influenza A ◽  
Respiratory Illness ◽  
Vaccine Effectiveness ◽  
Influenza Viruses ◽  
Point Estimate ◽  
Influenza B ◽  
Current Season ◽  
Immunization Registry

Abstract Background Due to marked variability in circulating influenza viruses each year, annual evaluation of the vaccine’s effectiveness against severe outcomes is essential. We used the Minnesota Department of Health’s (MDH) Severe Acute Respiratory Illness (SARI) surveillance to evaluate vaccine effectiveness (VE) against influenza-associated hospitalization over three influenza seasons. Methods Residual respiratory specimens from patients admitted with SARI were sent to the MDH laboratory for influenza RT-PCR testing. Medical records were reviewed to collect patient data. Vaccination history was verified using the state immunization registry. We included patients aged ≥6 months to &lt; 13 years, after which immunization reporting is not required, hospitalized from the earliest influenza detection after July through April each year. We defined vaccinated patients as those ≥1 dose of influenza vaccine in the current season. Children aged &lt; 9 years with no history of vaccination were considered vaccinated if 2 were doses given a month apart. Partially vaccinated children were excluded. We estimated VE as 1 minus the adjusted odds ratio (x100%) of influenza vaccination among influenza cases vs. negative controls, controlling for age, race, days from onset to admission, comorbidities, and admission month. Results Among 2198 SARI patients, 763 (35%) were vaccinated for influenza, 180 (8.2%) were partially vaccinated, and 1255 (57%) were unvaccinated. Influenza was detected among 202 (9.2%) children, and significantly more frequently among children aged ≥5 years (17%) compared with younger children (7.4%). The adjusted VE in 2013–14 was 68% (95% Confidence Interval: 34, 85), but was non-significant during the 2014–15 and 2015–16 seasons (Figure). Estimates of VE by influenza A subtypes varied substantially by year; VE against influenza B viruses was significant, but could not be stratified by year. VE was impacted when live attenuated influenza vaccine recipients were excluded. Conclusion We report moderately high influenza VE in 2013–14 and a point estimate higher than other published estimates from outpatient data in 2014–15. These results, underscore the importance of influenza vaccination to prevent severe outcomes such as hospitalization. Disclosures All authors: No reported disclosures.

scholarly journals 2553. Individual Patient-Level Data Meta-Analysis of Live Attenuated and Inactivated Influenza Vaccine Effectiveness Among US Children, 2013–2014 Through 2015–2016

2018 ◽  
Vol 5 (suppl_1) ◽  
pp. S68-S68
Author(s):  
Jessie Chung ◽  
Brendan Flannery ◽  
Rodolfo Begue ◽  
Herve Caspard ◽  
Laurie Demarcus ◽  
...  
Keyword(s):  
Influenza Vaccine ◽  
Influenza A ◽  
The United States ◽  
Vaccine Effectiveness ◽  
Vaccination Status ◽  
Influenza B ◽  
Rt Pcr ◽  
Current Season ◽  
Influenza A H1n1 ◽  
Vaccine Type

Abstract Background Quadrivalent live attenuated influenza vaccine (LAIV4) was not recommended for use in the United States for the 2016–2017 and 2017–2018 influenza seasons based on US observational studies of vaccine effectiveness (VE) from 2013–2014 to 2015–2016. We pooled individual patient data on children aged 2–17 years enrolled in 5 US studies during these 3 influenza seasons to further investigate VE by vaccine type. Methods Analyses included 17,173 children enrolled in the US Department of Defense Global Laboratory-based Influenza Surveillance Program, US Influenza Vaccine Effectiveness Network, Influenza Incidence Surveillance Project, Influenza Clinical Investigation for Children, and a Louisiana State University study. Participants’ specimens were tested for influenza by reverse transcription-polymerase chain reaction (RT-PCR), culture, or a combination of rapid antigen testing and RT-PCR. VE was calculated by comparing odds of vaccination with either inactivated influenza vaccine (IIV) or LAIV4 among influenza-positive cases to test-negative controls and calculated as 100 × (1 − odds ratio) in logistic regression models with age, calendar time, influenza season, and study site (random effect). Patients were stratified by prior season vaccination status in a subanalysis. Results Overall, 38% of patients (N = 6,558) were vaccinated in the current season, of whom 30% (N = 1,979) received LAIV4. Pooled VE of IIV against any influenza virus was 51% (95% CI: 47, 54) versus 26% (95% CI: 15, 36) for LAIV4. Point estimates for pooled VE against any influenza by age group ranged from 45% to 58% for IIV and 19% to 34% for LAIV4 during the 3 seasons (Figures 1 and 2). Pooled VE against influenza A(H1N1)pdm09 was 67% (95% CI: 62, 72) for IIV versus 20% (95% CI: −6, 39) for LAIV4. Pooled VE against influenza A(H3N2) was 29% (95% CI: 14, 42) for IIV versus 7% (95% CI: −11, 23) for LAIV4, and VE against influenza B was 52% (95% CI: 42, 60) for IIV and 66% (95% CI: 47, 77) for LAIV4. VE against influenza A(H1N1)pdm09 was lower for LAIV4 versus IIV across all strata of prior season vaccination (Figure 3). Conclusion Consistent with individual studies, our pooled analyses found that LAIV4 effectiveness was reduced for all age groups against influenza A(H1N1)pdm09 compared with IIV. This result did not vary based on prior vaccination status. Disclosures H. Caspard, AstraZeneca: Employee, Salary.

scholarly journals Influenza vaccine effectiveness in preventing hospitalisation of individuals 60 years of age and over with laboratory-confirmed influenza, Valencia Region, Spain, influenza season 2016/17

2018 ◽  
Vol 23 (8) ◽  
Author(s):  
Ainara Mira-Iglesias ◽  
F Xavier López-Labrador ◽  
Beatriz Guglieri-López ◽  
Miguel Tortajada-Girbés ◽  
Víctor Baselga-Moreno ◽  
...  
Keyword(s):  
Influenza Vaccine ◽  
Seasonal Influenza ◽  
Influenza Season ◽  
Respiratory Viruses ◽  
Vaccine Effectiveness ◽  
Surveillance Network ◽  
Current Season ◽  
Clinical Registries ◽  
The Impact ◽  
Multicentre Prospective Study

Introduction Seasonal influenza vaccination is widely recommended for people with risk factors, especially for people who are elderly. However, influenza vaccine effectiveness (IVE) varies year after year because of the variable antigenic composition of the circulating viruses and the vaccine composition. Methods: We summarise the results of IVE and the impact of previous vaccination among subjects 60 years of age and over in a multicentre prospective study in the Valencia Hospital Surveillance Network for the Study of Influenza and Respiratory Viruses Disease (VAHNSI) in Spain. We applied the test-negative design taking laboratory-confirmed influenza as outcome and vaccination status as exposure. Information about potential confounders was obtained from clinical registries or directly from patients. Results: Adjusted IVE was 19% (95% confidence interval (CI): −15 to 43). For patients vaccinated in the current season but not in the two previous seasons, effectiveness was 49% (95% CI: −20 to 78) and for patients vaccinated in the current and any of two previous seasons, effectiveness was 29% (95% CI: −3 to 52). For those patients not vaccinated in the current season but vaccinated in any of the two previous seasons, effectiveness was 53% (95% CI: 8 to 76). Conclusions: Our data show a low vaccine effectiveness for the 2016/17 influenza season.

scholarly journals Waning Vaccine Effectiveness Against Influenza-Associated Hospitalizations Among Adults, 2015–2016 to 2018–2019, United States Hospitalized Adult Influenza Vaccine Effectiveness Network

2021 ◽  
Author(s):  
Jill M Ferdinands ◽  
Manjusha Gaglani ◽  
Emily T Martin ◽  
Arnold S Monto ◽  
Donald Middleton ◽  
...  
Keyword(s):  
United States ◽  
Influenza Vaccine ◽  
Influenza A ◽  
Vaccine Effectiveness ◽  
Influenza B ◽  
Influenza A H1n1 ◽  
H3n2 Influenza

Abstract We observed decreased effectiveness of influenza vaccine with increasing time since vaccination for prevention of influenza A(H3N2), influenza A(H1N1)pdm09, and influenza B/Yamagata–associated hospitalizations among adults. Maximum vaccine effectiveness (VE) was observed shortly after vaccination, followed by an absolute decline in VE of about 8%–9% per month postvaccination.

scholarly journals Influenza vaccine effectiveness against hospitalization in the United States, 2019-2020

2020 ◽  
Author(s):  
Mark W Tenforde ◽  
H Keipp Talbot ◽  
Christopher H Trabue ◽  
Manjusha Gaglani ◽  
Tresa M McNeal ◽  
...  
Keyword(s):  
United States ◽  
Influenza Vaccine ◽  
Influenza Vaccination ◽  
Respiratory Illness ◽  
The United States ◽  
Vaccine Effectiveness ◽  
Influenza Viruses ◽  
Current Season ◽  
Hospital Resources ◽  
Negative Controls

Abstract Background Influenza causes significant morbidity and mortality and stresses hospital resources during periods of increased circulation. We evaluated the effectiveness of the 2019-2020 influenza vaccine against influenza-associated hospitalizations in the United States. Methods We included adults hospitalized with acute respiratory illness at 14 hospitals and tested for influenza viruses by reserve transcription polymerase chain reaction. Vaccine effectiveness (VE) was estimated by comparing the odds of current-season influenza vaccination in test-positive influenza cases versus test-negative controls, adjusting for confounders. VE was stratified by age and major circulating influenza types along with A(H1N1)pdm09 genetic subgroups. Results 3116 participants were included, including 18% (553) influenza-positive cases. Median age was 63 years. Sixty-seven percent (2079) received vaccination. Overall adjusted VE against influenza viruses was 41% (95% confidence interval [CI]: 27-52). VE against A(H1N1)pdm09 viruses was 40% (95% CI: 24-53) and 33% against B viruses (95% CI: 0-56). Of the two major A(H1N1)pdm09 subgroups (representing 90% of sequenced H1N1 viruses), VE against one group (5A+187A,189E) was 59% (95% CI: 34-75) whereas no significant VE was observed against the other group (5A+156K) [-1%, 95% CI: -61-37]. Conclusions In a primarily older population, influenza vaccination was associated with a 41% reduction in risk of hospitalized influenza illness.

scholarly journals Retraction Note: The impact of repeated vaccination on influenza vaccine effectiveness: a systematic review and meta-analysis

BMC Medicine ◽  
2018 ◽  
Vol 16 (1) ◽  
Author(s):  
Lauren C. Ramsay ◽  
Sarah A. Buchan ◽  
Robert G. Stirling ◽  
Benjamin J. Cowling ◽  
Shou Feng ◽  
...  
Keyword(s):  
Systematic Review ◽  
Influenza Vaccine ◽  
Meta Analysis ◽  
Vaccine Effectiveness ◽  
The Impact

Vaccination Schedules

2019 ◽  
Author(s):  
Gee Yen Shin
Keyword(s):  
Hepatitis B ◽  
Influenza Vaccine ◽  
Influenza A ◽  
Online Version ◽  
Influenza B ◽  
Immunisation Schedule ◽  
Influenza A H1n1 ◽  
Green Book ◽  
H3n2 Influenza ◽  
The Uk

The vaccines included in the current UK Immunisation Schedule offer protection against the following pathogens: A. Viruses ● Measles ● Mumps ● Rubella ● Polio ● Human Papilloma Virus (certain serotypes) ● Rotavirus ● Influenza virus (flu A and B) ● Varicella zoster virus (shingles) ● Hepatitis B virus B. Bacteria ● Corynebacterium diphtheriae (Diphtheria) ● Clostridium tetani (Tetanus) ● Bordetella pertussis (Pertussis) ● Haemophilus influenzae type B (Hib) ● Neisseria meningitidis (Meningococcal disease—certain serotypes) ● Streptococcus pneumoniae (Pneumococcal disease—certain serotypes) The UK Immunisation Schedule has evolved over several decades and reflects changes in vaccine development and commercial availability, national and sometimes international disease epidemiology, and the latest expert opinion. It is designed to offer optimal protection against infectious diseases of childhood to infants and children at the most appropriate age. The most up-to-date information about the UK Immunisation Schedule is available on the online version of the Department of Health publication commonly known as the ‘Green Book’: Immunisation Against Infectious Disease Handbook (see Further reading. Various chapters of the online version are updated at regular intervals; thus, it is very important to refer to the online version of the Green Book on the website for current guidance. Changes to the UK Immunisation Schedule are made on the recommendation of the independent Joint Committee on Vaccines and Immunisation (JCVI). Several of the UK Immunisation Schedule vaccines are combined vaccines: ● Measles, mumps, and rubella (MMR). ● Hexavalent diphtheria, tetanus, acellular pertussis, inactivated polio virus, Haemophilus influenza type b, hepatitis B (DTaP/IPV/Hib/HepB). ● Diphtheria, tetanus, acellular pertussis, inactivated polio, and Haemophilus influenzae (DTaP/IPV/Hib). ● Diphtheria, tetanus, acellular pertussis, inactivated polio (DTaP/IPV). ● Tetanus, diphtheria, and inactivated polio (Td/IPV). ● Inactivated influenza vaccine: influenza A H1N1, H3N2, influenza B. ● Live attenuated intranasal influenza vaccine: influenza A H1N1, H3N2, influenza B. In the UK, vaccines against single pathogens covered by the MMR vaccine are not recommended and not available in the National Health Service (NHS). There has been some limited demand for single-target vaccines, e.g. measles, due to misguided and unfounded concerns about the alleged risks of autism following MMR.

scholarly journals 992. 2016–2017 Influenza Burden of Disease and End-of-Season Influenza Vaccine Effectiveness (VE) Estimates for Preventing Influenza-Related Hospitalization Among Canadian Adults: An Analysis From the Canadian Immunization Research Network (CIRN) Serious Outcomes Surveillance (SOS) Network

2018 ◽  
Vol 5 (suppl_1) ◽  
pp. S293-S294
Author(s):  
Michaela Nichols ◽  
Melissa K Andrew ◽  
Todd F Hatchette ◽  
Ardith Ambrose ◽  
Guy Boivin ◽  
...  
Keyword(s):  
Clinical Trials ◽  
Influenza Vaccine ◽  
Active Surveillance ◽  
Burden Of Disease ◽  
Influenza A ◽  
Conditional Logistic Regression ◽  
Vaccine Effectiveness ◽  
Research Network ◽  
Nasopharyngeal Swab ◽  
Research Grant

Abstract Background To inform public health decision making around influenza prevention and treatment, ongoing surveillance of the influenza burden of disease and assessment of influenza vaccine effectiveness (VE) is critical. The Canadian Immunization Research Network (CIRN) Serious Outcomes Surveillance (SOS) Network conducts active surveillance each influenza season to characterize the burden of influenza disease and to provide estimates of influenza VE to prevent influenza-related hospitalization in Canadian adults (≥16 years of age). Methods Active surveillance for influenza was conducted at 13 hospitals in four provinces beginning on November 15, 2016 and ending April 30, 2017. Patients admitted with any respiratory diagnosis or symptom were eligible for enrolment. Eligible patients had a nasopharyngeal swab collected and tested for influenza using polymerase chain reaction (PCR). Patients who tested positive for influenza were considered cases; patients who tested negative for influenza were eligible to become matched controls. Detailed demographic and medical information were obtained from the medical record. Influenza VE was estimated as 1 − odds ratio (OR) of influenza in vaccinated vs. unvaccinated patients × 100% using conditional logistic regression, with corresponding 95% confidence intervals (CIs). Results A total of 1,431 influenza cases were enrolled; the majority were influenza A (n = 1,299) and 100% of patients with known influenza A subtype were A/H3N2. Among all influenza cases, 144 (10.1%) patients were admitted to the intensive care unit (ICU) and 91 (6.4%) patients died within 30 days of discharge. Overall adjusted influenza VE for prevention of influenza-related hospitalization in all ages was 23.3% (95% CI: 2.9–39.4%), with slightly lower VE observed in patients ≥65 years (VE: 19.4%; 95% CI: −7.8–39.8%) and higher VE observed in patients &lt;65 years (VE: 47.9%; 95% CI: 9.9–69.9%). Conclusion Overall, influenza VE was low but effective (VE: 23%) for preventing influenza-related hospitalization during the 2016–2017 season in Canada. Given the low influenza VE observed, continued assessment of influenza VE is crucial to inform immunization policy in Canada and to emphasize the importance of the development and utilization of improved influenza vaccines. Disclosures M. K. Andrew, GSK: Grant Investigator, Research grant. Pfizer: Grant Investigator, Research grant. sanofi pasteur: Grant Investigator, Research grant. T. F. Hatchette, GSK: Grant Investigator, Research grant. Pfizer: Grant Investigator, Research grant. Abbvie: Consultant, Speaker honorarium. J. McElhaney, GSK: Scientific Advisor, Speaker honorarium. sanofi pasteur: Scientific Advisor, Speaker honorarium. A. McGeer, GSK: Grant Investigator, Research grant. Hoffman La Roche: Grant Investigator, Research grant. sanofi pasteur: Grant Investigator, Research grant. A. Poirier, sanofi pasteur: Investigator, Research grant. Actelion: Grant Investigator, Research grant. J. Powis, GSK: Grant Investigator, Research grant. Merck: Grant Investigator, Research grant. Roche: Grant Investigator, Research grant. Synthetic Biologics: Investigator, Grant recipient. M. Semret, GSK: Grant Investigator, Research grant. Pfizer: Grant Investigator, Research grant. S. Trottier, CIHR: Grant Investigator, Research grant. S. A. McNeil, GSK: Grant Investigator, Research grant. Pfizer: Grant Investigator, Research grant. Merck: Collaborator and Consultant, Contract clinical trials and Speaker honorarium. Novartis: Collaborator, Contract clinical trials. sanofi pasteur: Collaborator, Contract clinical trials.

Influenza Vaccine Effectiveness Among Children for the 2017–2018 Season

2019 ◽  
Vol 9 (4) ◽  
pp. 468-473 ◽  
Author(s):  
Lauren N Powell ◽  
Rodolfo E Bégué
Keyword(s):  
Influenza Vaccine ◽  
Influenza A ◽  
Influenza Season ◽  
Vaccine Effectiveness ◽  
Influenza B ◽  
Immunization Registry ◽  
Previous Season ◽  
Waning Immunity ◽  
Small Benefit ◽  
Susceptible Populations

Abstract Background The 2017–2018 influenza season was of high severity. Circulating influenza strains change periodically, making it important to determine vaccine effectiveness on an annual basis, especially for susceptible populations. The primary aim of our study was to estimate the effectiveness of the influenza vaccine among children. Secondary aims were to assess the effect of previous season vaccination and intraseasonal waning of immunity. Methods Children 6 months to 17 years of age tested for influenza during the 2017–2018 season were included. Clinical charts were reviewed, and immunization status was confirmed via the Louisiana Immunization Registry. Influenza vaccine effectiveness (IVE) was estimated in a test-negative design by comparing vaccination status of influenza-positive vs influenza-negative cases. Results A total of 3595 children were included, 26% of whom tested positive for influenza, mostly type A (79%); 15% had received an influenza vaccine prior to illness: 8% among the influenza-positive and 17% among influenza-negative cases (P &lt;.0001). IVE for the 2017–2018 influenza season was 52% overall (95% confidence interval, 38%–62%), 49% for influenza A, and 60% for influenza B. While receiving current year (2017–2018) vaccine had the most effect, receiving the previous year (2016–2017) vaccine had a small benefit and no interference. We found no evidence of waning immunity of the vaccine for the 2017–2018 season. Conclusions IVE was moderate for children. Previous year vaccination had a small but significant benefit and there was no evidence of waning immunity in our cohort. Ongoing national and local surveillance is important to understand the benefit of influenza vaccination.

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