Clinical and Economic Outcomes Associated with Cell-Based Quadrivalent Influenza Vaccine vs. Standard-Dose Egg-Based Quadrivalent Influenza Vaccines during the 2018–19 Influenza Season in the United States

Non-egg-based influenza vaccines eliminate the potential for egg-adapted mutations and potentially increase vaccine effectiveness. This retrospective study compared hospitalizations/emergency room (ER) visits and all-cause annualized healthcare costs among subjects aged 4–64 years who received cell-based quadrivalent (QIVc) or standard-dose egg-based quadrivalent (QIVe-SD) influenza vaccine during the 2018–19 influenza season. Administrative claims data (IQVIA PharMetrics® Plus, IQVIA, USA) were utilized to evaluate clinical and economic outcomes. Adjusted relative vaccine effectiveness (rVE) of QIVc vs. QIVe-SD among overall cohort, as well as for three subgroups (age 4–17 years, age 18–64 years, and high-risk) was evaluated using inverse probability of treatment weighting (IPTW) and Poisson regression models. Generalized estimating equation models among the propensity score matched sample were used to estimate annualized all-cause costs. A total of 669,030 recipients of QIVc and 3,062,797 of QIVe-SD were identified after IPTW adjustments. Among the overall cohort, QIVc had higher adjusted rVEs against hospitalizations/ER visits related to influenza, all-cause hospitalizations, and hospitalizations/ER visits associated with any respiratory event compared to QIVe-SD. The adjusted annualized all-cause total costs were higher for QIVe-SD compared to QIVc ((+$461); p < 0.05).

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A Real-World Clinical and Economic Analysis of Cell-derived Quadrivalent Influenza Vaccine Compared to Standard Egg-derived Quadrivalent Influenza Vaccines During the 2019-20 Influenza Season in the United States

Open Forum Infectious Diseases ◽

10.1093/ofid/ofab604 ◽

2021 ◽

Author(s):

Victoria Divino ◽

Vamshi Ruthwik Anupindi ◽

Mitch DeKoven ◽

Joaquin Mould-Quevedo ◽

Stephen I Pelton ◽

...

Keyword(s):

High Risk ◽

Influenza Vaccine ◽

Influenza Season ◽

The United States ◽

Vaccine Effectiveness ◽

Influenza Vaccines ◽

Sensitivity Analyses ◽

Administrative Claims ◽

Adaptive Mutations ◽

Quadrivalent Influenza Vaccine

Abstract Background Cell-derived influenza vaccines are not subject to egg adaptive mutations that have potential to decrease vaccine effectiveness. This retrospective analysis estimated the relative vaccine effectiveness (rVE) of cell-derived quadrivalent influenza vaccine (IIV4c) compared to standard egg-derived quadrivalent influenza vaccines (IIV4e) among recipients aged 4-64 years in the US during the 2019-20 influenza season. Methods The IQVIA PharMetrics® Plus administrative claims database was utilized. Study outcomes were assessed post-vaccination through the end of the study period (March 7, 2020). Inverse probability of treatment weighting (IPTW) was implemented to adjust for covariate imbalance. Adjusted rVE against influenza-related hospitalizations/emergency room (ER) visits and other clinical outcomes was estimated through IPTW-weighted Poisson regression models for the IIV4c and IIV4e cohorts and for the subgroup with ≥1 high-risk condition. Sensitivity analyses modifying the outcome assessment period as well as a doubly-robust analysis were also conducted. IPTW-weighted generalized linear models were used to estimate predicted annualized all-cause costs. Results The final sample comprised 1,138,969 IIV4c and 3,926,357 IIV4e recipients following IPTW adjustment. IIV4c was more effective in preventing influenza-related hospitalizations/ER visits as well as respiratory-related hospitalizations/ER visits compared to IIV4e. IIV4c was also more effective for the high-risk subgroup and across the sensitivity analyses. IIV4c was also associated with significantly lower annualized all-cause total costs compared to IIV4e (-$467), driven by lower costs for outpatient medical services and inpatient hospitalizations. Conclusions IIV4c was significantly more effective in preventing influenza-related hospitalizations/ER visits compared to IIV4e and was associated with significantly lower all-cause costs.

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1341. Relative Vaccine Effectiveness Against Influenza-related Hospitalizations and Respiratory Events During the 2019/20 Influenza seAson in U.S. Children and Adults. A Real-World Evidence Comparison Between Quadrivalent Cell-based and Egg-based Influenza Vaccines

Open Forum Infectious Diseases ◽

10.1093/ofid/ofab466.1533 ◽

2021 ◽

Vol 8 (Supplement_1) ◽

pp. S758-S758

Author(s):

Stephen I Pelton ◽

Maarten Postma ◽

Victoria Divino ◽

Joaquin F Mould-Quevedo ◽

Ruthwik Anupindi ◽

...

Keyword(s):

High Risk ◽

Influenza Vaccine ◽

Influenza Season ◽

Standard Dose ◽

The United States ◽

Negative Control ◽

Vaccine Effectiveness ◽

Administrative Claims ◽

Real World Evidence ◽

Quadrivalent Influenza Vaccine

Abstract Background Non-egg-based influenza vaccine manufacturing reduces egg adaptation and therefore has the potential to increase vaccine effectiveness. This study evaluated whether the cell-based quadrivalent influenza vaccine (QIVc) improved relative vaccine effectiveness (rVE) compared to standard-dose egg-based quadrivalent influenza vaccine (QIVe-SD) in the reduction of influenza-related and respiratory-related hospitalizations/emergency room (ER) visits among subjects 4-64 years old during the 2019/20 influenza season. Methods A retrospective analysis was conducted among subjects 4-64 years old vaccinated with QIVc or QIVe-SD using administrative claims data in the United States of America (U.S.) (IQVIA PharMetrics® Plus). Inverse probability of treatment weighting (IPTW) was used to adjust for baseline confounders. Post-IPTW, the number of events and rates (per 1,000 vaccinated subject-seasons) of influenza-related hospitalizations/ER visits, respiratory-related hospitalizations/ER visits and all-cause hospitalizations were assessed. Poisson regression was used to estimate adjusted rVE. To avoid any influenza outcome misclassification with COVID-19 infection, the study period ended March 7,2020. A sub-analysis for a high-risk subgroup was conducted. Urinary tract infection (UTI) hospitalization was assessed as a negative control endpoint. Results During the 2019/20 influenza season, 1,150,134 QIVc and 3,924,819 QIVe-SD recipients were identified post-IPTW. Overall adjusted analyses (4-64 years old) found that QIVc was associated with a significantly higher rVE compared to QIVe-SD against influenza-related hospitalizations/ER visits (5.3% [95% CI: 0.5%-9.9%]), all-cause hospitalizations (14.5% [95% CI: 13.1%-15.8%]) and any respiratory-related hospitalization/ER visit (8.2% [95% CI: 6.5%-9.8%]). A similar trend was seen for the high-risk subgroup; for instance, rVE for QIVc compared to QIVe-SD against influenza-related hospitalizations/ER visits was 10.5% [95% CI: 2.9%-17.4%]. No effect was identified for the negative control outcome. Conclusion QIVc was significantly more effective in preventing influenza-related and respiratory-related hospitalizations/ER visits, as well as all-cause hospitalizations, compared to QIVe-SD. Disclosures Stephen I. Pelton, MD, Seqirus (Consultant) Maarten Postma, Dr., Seqirus (Consultant) Victoria Divino, PhD, Seqirus (Consultant) Joaquin F. Mould-Quevedo, PhD, Seqirus (Employee) Ruthwik Anupindi, PhD, Seqirus (Consultant) Mitchell DeKoven, PhD, Seqirus (Consultant) myron J. levin, MD, GSK group of companies (Employee, Research Grant or Support)

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LB14. Safety and Immunogenicity of High-Dose Quadrivalent Influenza Vaccine Administered by Intramuscular Route in Subjects Aged 65 Years and Older

Open Forum Infectious Diseases ◽

10.1093/ofid/ofy229.2188 ◽

2018 ◽

Vol 5 (suppl_1) ◽

pp. S764-S764 ◽

Cited By ~ 1

Author(s):

Lee-Jah Chang ◽

Ya Meng ◽

Helene Janosczyk ◽

Victoria Landolfi ◽

H Keipp Talbot ◽

...

Keyword(s):

United States ◽

Immune Response ◽

Influenza Vaccine ◽

Standard Dose ◽

The United States ◽

Influenza Vaccines ◽

High Dose ◽

Post Vaccination ◽

B Lineage ◽

Research Grant

Abstract Background Older adults (≥65 years of age) remain at increased risk of influenza because they do not respond to standard dose influenza vaccines as well as younger adults. A high dose, inactivated trivalent influenza vaccine, IIV3-HD, containing four times the antigen content (60 µg hemagglutinin per influenza strain) of standard-dose influenza vaccines has been available in the United States since 2010. Two distinct B influenza lineages (Victoria and Yamagata) have co-circulated for over a decade, making it difficult to predict which will predominate the next season. IIV4-HD has been developed to address the frequent influenza B strain mismatches by incorporating a strain from each B lineage. This pivotal Phase III study evaluated the safety and immunogenicity of IIV4-HD as compared with two IIV3-HD vaccines. Method A randomized, modified double-blind, multicenter study (NCT03282240) was conducted in 2670 healthy subjects in the United States, who were randomly assigned to receive IIV4-HD, a licensed IIV3-HD, or an IIV3-HD with the alternate B influenza strain. Using the hemagglutinin inhibition (HAI) assay at baseline and 28 days after vaccination, post-vaccination geometric mean titers and seroconversion rates were measured. Safety data were collected through 6 months post-vaccination. Result IIV4-HD was noninferior to the licensed IIV3-HD and the investigational IIV3-HD (containing the alternate B strain) for all four influenza strains as assessed by HAI GMTs and seroconversion rates. Moreover, IIV4-HD induced a superior immune response (HAI GMTs and seroconversion rates) compared with the immune response induced by the IIV3-HD that does not contain the corresponding B strain. Reactogenicity profiles were comparable across all study groups. Most unsolicited adverse events were of Grade 1 or Grade 2 intensity. One serious adverse event considered related by the Investigator was reported in the IIV4-HD group. Conclusion Vaccination of adults 65 years of age and older with IIV4-HD was found to be noninferior to two IIV3-HD vaccines with a similar safety profile. The addition of a second B lineage strain does not adversely affect the safety or immunogenicity profile of IIV4-HD compared with IIV3-HD. Disclosures L. J. Chang, Sanofi Pasteur: Employee, Salary. Y. Meng, Sanofi Pasteur: Employee, Salary. H. Janosczyk, Sanofi Pasteur: Employee, Salary. V. Landolfi, Sanofi Pasteur: Employee, Salary. H. K. Talbot, Sanofi Pasteur: Investigator, Research grant. Gilead: Investigator, Research grant. MedImmune: Investigator, Research grant. Vaxinnate: Safety Board, none. Seqirus: Safety Board, none.

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150. Relative Effectiveness of High-Dose and Standard-Dose Influenza Vaccine Against Influenza-Related Hospitalization Among Older Adults—United States, 2015–2017

Open Forum Infectious Diseases ◽

10.1093/ofid/ofy209.020 ◽

2018 ◽

Vol 5 (suppl_1) ◽

pp. S10-S10

Author(s):

Joshua Doyle ◽

Lauren Beacham ◽

Elif Alyanak ◽

Manjusha Gaglani ◽

Emily T Martin ◽

...

Keyword(s):

United States ◽

Older Adults ◽

Influenza Vaccine ◽

Influenza A ◽

Standard Dose ◽

Relative Effectiveness ◽

The United States ◽

Vaccine Effectiveness ◽

High Dose ◽

Research Grant

Abstract Background Seasonal influenza causes substantial morbidity and mortality, and older adults are disproportionately affected. Newer vaccines have been developed for use in people 65 years and older, including a trivalent inactivated vaccine with a 4-fold higher dose of antigen (IIV-HD). In recent years, the use of IIV-HD has increased sufficiently to evaluate its effectiveness compared with standard-dose inactivated influenza vaccines (IIV-SD). Methods Hospitalized patients with acute respiratory illness were enrolled in an observational vaccine effectiveness study at 8 hospitals in 4 states participating in the United States Hospitalized Adult Influenza Vaccine Effectiveness Network during the 2015–2016 and 2016–2017 influenza seasons. Predominant influenza A virus subtypes were H1N1 and H3N2, respectively, during these seasons. All enrolled patients were tested for influenza virus with polymerase chain reaction. Receipt and type of influenza vaccine was determined from electronic records and chart review. Odds of laboratory-confirmed influenza were compared among vaccinated and unvaccinated patients. Relative odds of laboratory-confirmed influenza were determined for patients who received IIV-HD or IIV-SD, and adjusted for potential confounding variables via logistic regression. Results Among 1,744 enrolled patients aged ≥ 65 years, 1,105 (63%) were vaccinated; among those vaccinated, 621 (56%) received IIV-HD and 484 (44%) received IIV-SD. Overall, 315 (18%) tested positive for influenza, including 97 (6%) who received IIV-HD, 86 (5%) who received IIV-SD, and 132 (8%) who were unvaccinated. Controlling for age, race, sex, enrollment site, date of illness, index of comorbidity, and influenza season, the adjusted odds of influenza among patients vaccinated with IIV-HD vs. IIV-SD were 0.72 (P = 0.06, 95% CI: 0.52 to 1.01). Conclusion Comparison of high-dose vs. standard-dose vaccine effectiveness during 2 recent influenza seasons (1 H1N1 and 1 H3N2-predominant) suggested relative benefit (nonsignificant) of high-dose influenza vaccine in protecting against influenza-associated hospitalization among persons aged 65 years and older; additional years of data are needed to confirm this finding. Disclosures H. K. Talbot, sanofi pasteur: Investigator, Research grant. Gilead: Investigator, Research grant. MedImmune: Investigator, Research grant. Vaxinnate: Safety Board, none. Seqirus: Safety Board, none.

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Effects of Influenza Vaccination in the United States During the 2018–2019 Influenza Season

Clinical Infectious Diseases ◽

10.1093/cid/ciz1244 ◽

2020 ◽

Vol 71 (8) ◽

pp. e368-e376 ◽

Cited By ~ 7

Author(s):

Jessie R Chung ◽

Melissa A Rolfes ◽

Brendan Flannery ◽

Pragati Prasad ◽

Alissa O’Halloran ◽

...

Keyword(s):

United States ◽

Influenza Vaccine ◽

Influenza Vaccination ◽

Influenza Season ◽

The United States ◽

Vaccine Effectiveness ◽

Influenza Viruses ◽

Monte Carlo Algorithm ◽

Medical Visits ◽

The Us

Abstract Background Multivalent influenza vaccine products provide protection against influenza A(H1N1)pdm09, A(H3N2), and B lineage viruses. The 2018–2019 influenza season in the United States included prolonged circulation of A(H1N1)pdm09 viruses well-matched to the vaccine strain and A(H3N2) viruses, the majority of which were mismatched to the vaccine. We estimated the number of vaccine-prevented influenza-associated illnesses, medical visits, hospitalizations, and deaths for the season. Methods We used a mathematical model and Monte Carlo algorithm to estimate numbers and 95% uncertainty intervals (UIs) of influenza-associated outcomes prevented by vaccination in the United States. The model incorporated age-specific estimates of national 2018–2019 influenza vaccine coverage, influenza virus–specific vaccine effectiveness from the US Influenza Vaccine Effectiveness Network, and disease burden estimated from population-based rates of influenza-associated hospitalizations through the Influenza Hospitalization Surveillance Network. Results Influenza vaccination prevented an estimated 4.4 million (95%UI, 3.4 million–7.1 million) illnesses, 2.3 million (95%UI, 1.8 million–3.8 million) medical visits, 58 000 (95%UI, 30 000–156 000) hospitalizations, and 3500 (95%UI, 1000–13 000) deaths due to influenza viruses during the US 2018–2019 influenza season. Vaccination prevented 14% of projected hospitalizations associated with A(H1N1)pdm09 overall and 43% among children aged 6 months–4 years. Conclusions Influenza vaccination averted substantial influenza-associated disease including hospitalizations and deaths in the United States, primarily due to effectiveness against A(H1N1)pdm09. Our findings underscore the value of influenza vaccination, highlighting that vaccines measurably decrease illness and associated healthcare utilization even in a season in which a vaccine component does not match to a circulating virus.

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Relative and Absolute Effectiveness of High-Dose and Standard-Dose Influenza Vaccine Against Influenza-Related Hospitalization Among Older Adults—United States, 2015–2017

Clinical Infectious Diseases ◽

10.1093/cid/ciaa160 ◽

2020 ◽

Cited By ~ 3

Author(s):

Joshua D Doyle ◽

Lauren Beacham ◽

Emily T Martin ◽

H Keipp Talbot ◽

Arnold Monto ◽

...

Keyword(s):

United States ◽

Older Adults ◽

Influenza Vaccine ◽

Standard Dose ◽

Relative Effectiveness ◽

Respiratory Illness ◽

The United States ◽

Vaccine Effectiveness ◽

High Dose ◽

Confounding Variables

Abstract Background Seasonal influenza causes substantial morbidity and mortality in older adults. High-dose inactivated influenza vaccine (HD-IIV), with increased antigen content compared to standard-dose influenza vaccines (SD-IIV), is licensed for use in people aged ≥65 years. We sought to evaluate the effectiveness of HD-IIV and SD-IIV for prevention of influenza-associated hospitalizations. Methods Hospitalized patients with acute respiratory illness were enrolled in an observational vaccine effectiveness study at 8 hospitals in the United States Hospitalized Adult Influenza Vaccine Effectiveness Network during the 2015–2016 and 2016–2017 influenza seasons. Enrolled patients were tested for influenza, and receipt of influenza vaccine by type was recorded. Effectiveness of SD-IIV and HD-IIV was estimated using a test-negative design (comparing odds of influenza among vaccinated and unvaccinated patients). Relative effectiveness of SD-IIV and HD-IIV was estimated using logistic regression. Results Among 1487 enrolled patients aged ≥65 years, 1107 (74%) were vaccinated; 622 (56%) received HD-IIV, and 485 (44%) received SD-IIV. Overall, 277 (19%) tested positive for influenza, including 98 (16%) who received HD-IIV, 87 (18%) who received SD-IIV, and 92 (24%) who were unvaccinated. After adjusting for confounding variables, effectiveness of SD-IIV was 6% (95% confidence interval [CI] −42%, 38%) and that of HD-IIV was 32% (95% CI −3%, 54%), for a relative effectiveness of HD-IIV versus SD-IIV of 27% (95% CI −1%, 48%). Conclusions During 2 US influenza seasons, vaccine effectiveness was low to moderate for prevention of influenza hospitalization among adults aged ≥65 years. High-dose vaccine offered greater effectiveness. None of these findings were statistically significant.

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Successes and failures of the live-attenuated influenza vaccine, can we do better?

10.1101/424275 ◽

2018 ◽

Author(s):

Laura Matrajt ◽

M. Elizabeth Halloran ◽

Rustom Antia

Keyword(s):

United States ◽

Influenza Vaccine ◽

Mathematical Models ◽

Viral Infections ◽

Influenza Season ◽

The United States ◽

Vaccine Effectiveness ◽

Effective Protection ◽

Live Attenuated Vaccines ◽

Live Attenuated Influenza Vaccine

Live-attenuated vaccines are usually highly effective against many acute viral infections. However, the effective- ness of the live attenuated influenza vaccine (LAIV) can vary widely, ranging from 0% effectiveness in some studies done in the United States to 50% in studies done in Europe. The reasons for these discrepancies remain largely unclear. In this paper we use mathematical models to explore how the efficacy of LAIV is affected by the degree of mismatch with the currently circulating influenza strain and interference with pre-existing immunity. The model incorporates two key antigenic distances - the distance between pre-existing immunity and the currently circulating strain as well as the LAIV strain. Our models show that a LAIV that is matched with the currently circulating strain is likely to have only modest efficacy. Our results suggest that the efficacy of the vaccine would be increased (optimized) if, rather than being matched to the circulating strain, it is antigenically slightly further from pre-existing immunity compared with the circulating strain. The models also suggest two regimes in which LAIV that is matched to circulating strains may provide effective protection. The first is in children before they have built immunity from circulating strains. The second is in response to novel strains (such as antigenic shifts) which are at substantial antigenic distance from previously circulating strains. Our models provide an explanation for the variation in vaccine effectiveness, both between children and adults as well as between studies of vaccine effectiveness observed during the 2014-15 influenza season in different countries.

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Influenza vaccines: the potential benefits of cell-culture isolation and manufacturing

Therapeutic Advances in Vaccines and Immunotherapy ◽

10.1177/2515135520908121 ◽

2020 ◽

Vol 8 ◽

pp. 251513552090812

Author(s):

Sankarasubramanian Rajaram ◽

Constantina Boikos ◽

Daniele K. Gelone ◽

Ashesh Gandhi

Keyword(s):

Cell Culture ◽

Influenza Vaccine ◽

Vaccine Development ◽

The United States ◽

Vaccine Effectiveness ◽

Influenza Vaccines ◽

World Health ◽

Severe Illness ◽

Vaccine Production ◽

Culture Technology

Influenza continues to cause severe illness in millions and deaths in hundreds of thousands annually. Vaccines are used to prevent influenza outbreaks, however, the influenza virus mutates and annual vaccination is required for optimal protection. Vaccine effectiveness is also affected by other potential factors such as the human immune system, a mismatch with the chosen candidate virus, and egg adaptation associated with egg-based vaccine production. This article reviews the influenza vaccine development process and describes the implications of the changes to the cell-culture process and vaccine strain recommendations by the World Health Organization since the 2017 season. The traditional manufacturing process for influenza vaccines relies on fertilized chicken eggs that are used for vaccine production. Vaccines must be produced in large volumes and the complete process requires approximately 6 months for the egg-based process. In addition, egg adaptation of seed viruses occurs when viruses adapt to avian receptors found within eggs to allow for growth in eggs. These changes to key viral antigens may result in antigenic mismatch and thereby reduce vaccine effectiveness. By contrast, cell-derived seed viruses do not require fertilized eggs and eliminate the potential for egg-adapted changes. As a result, cell-culture technology improves the match between the vaccine virus strain and the vaccine selected strain, and has been associated with increased vaccine effectiveness during a predominantly H3N2 season. During the 2017–2018 influenza season, a small number of studies conducted in the United States compared the effectiveness of egg-based and cell-culture vaccines and are described here. These observational and retrospective studies demonstrate that inactivated cell-culture vaccines were more effective than egg-based vaccines. Adoption of cell-culture technology for influenza vaccine manufacturing has been reported to improve manufacturing efficiency and the additional benefit of improving vaccine effectiveness is a key factor for future policy making considerations.

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Effectiveness of the Cell–Derived Inactivated Quadrivalent Influenza Vaccine in Individuals at High Risk of Influenza Complications in the 2018-2019 US Influenza Season

Open Forum Infectious Diseases ◽

10.1093/ofid/ofab167 ◽

2021 ◽

Author(s):

Constantina Boikos ◽

Mahrukh Imran ◽

Van Hung Nguyen ◽

Thierry Ducruet ◽

Gregg C Sylvester ◽

...

Keyword(s):

High Risk ◽

Influenza Vaccine ◽

Influenza Season ◽

Health Condition ◽

Geographic Region ◽

Vaccine Effectiveness ◽

Influenza Viruses ◽

Influenza Vaccines ◽

Study Cohort ◽

Medical Conditions

Abstract Background Higher rates of influenza-related morbidity and mortality occur in individuals with underlying medical conditions. To improve vaccine effectiveness, cell-based technology for influenza vaccine manufacturing has been developed. Cell–derived inactivated quadrivalent influenza vaccines (cIIV4) may improve protection in seasons where egg-propagated influenza viruses undergo mutations that affect antigenicity. This study aimed to estimate the relative vaccine effectiveness (rVE) of cIIV4 versus egg-derived inactivated quadrivalent influenza vaccines (eIIV4) in preventing influenza-related medical encounters in individuals with underlying medical conditions putting them at high risk of influenza complications during the 2018-2019 U.S. influenza season. Methods An integrated dataset, linking primary care electronic medical records with claims data, was used to conduct a retrospective cohort study among individuals aged ≥4 years, with ≥1 health condition, vaccinated with cIIV4 or eIIV4 during the 2018-2019 season. Adjusted odds ratios (ORs) were derived using a doubly robust inverse probability of treatment-weighting (IPTW) model, adjusting for age, sex, race, ethnicity, geographic region, vaccination week, and health status. rVE was estimated by (1- OR)*100 and presented with 95% confidence intervals (CI). Results The study cohort included 471,301 cIIV4 and 1,641,915 eIIV4 recipients. Compared with eIIV4, cIIV4 prevented significantly more influenza-related medical encounters among individuals with ≥1 health condition (rVE 13.4% [95% CI 11.4-15.4]); chronic pulmonary disease (18.7% [16.0-21.3]); and rheumatic disease (11.8% [3.6-19.3]). Conclusions Our findings support the use of cIIV4 in individuals ≥4 years of age at high risk of influenza complications and provide further evidence supporting improved effectiveness of cIIV4 compared to eIIV4.

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Rapid assessment of influenza vaccine effectiveness: analysis of an internet-based cohort

Epidemiology and Infection ◽

10.1017/s0950268811001804 ◽

2011 ◽

Vol 140 (7) ◽

pp. 1309-1315 ◽

Cited By ~ 20

Author(s):

K. T. D. EAMES ◽

E. BROOKS-POLLOCK ◽

D. PAOLOTTI ◽

M. PEROSA ◽

C. GIOANNINI ◽

...

Keyword(s):

Influenza Vaccine ◽

Pandemic Influenza ◽

Seasonal Influenza ◽

Influenza Season ◽

Rapid Assessment ◽

Vaccine Effectiveness ◽

Influenza Vaccines ◽

Seasonal Influenza Vaccine ◽

Effectiveness Analysis ◽

Self Reports

SUMMARYThe effectiveness of influenza vaccination programmes is seldom known during an epidemic. We developed an internet-based system to record influenza-like symptoms and response to infection in a participating cohort. Using self-reports of influenza-like symptoms and of influenza vaccine history and uptake, we estimated vaccine effectiveness (VE) without the need for individuals to seek healthcare. We found that vaccination with the 2010 seasonal influenza vaccine was significantly protective against influenza-like illness (ILI) during the 2010–2011 influenza season (VE 52%, 95% CI 27–68). VE for individuals who received both the 2010 seasonal and 2009 pandemic influenza vaccines was 59% (95% CI 27–77), slightly higher than VE for those vaccinated in 2010 alone (VE 46%, 95% CI 9–68). Vaccinated individuals with ILI reported taking less time off work than unvaccinated individuals with ILI (3·4 days vs. 5·3 days, P<0·001).

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