The effectiveness of seasonal trivalent inactivated influenza vaccine in preventing laboratory confirmed influenza hospitalisations in Auckland, New Zealand in 2012

doi:10.1016/j.vaccine.2014.04.013

Vaccine

Volume 32, Issue 29, 17 June 2014, Pages 3687-3693

https://doi.org/10.1016/j.vaccine.2014.04.013 Get rights and content

Highlights

•
This study adds to the limited research on VE to influenza from the southern hemisphere.
•
TIV vaccines show low to moderate protection against influenza positive hospitalisation in 2012.
•
VE varied by influenza type and subtype.
•
Vaccination appeared to be less effective in patients aged 65 years and older.
•
Older people did not appear to be significantly protected against infection with influenza A (H3N2).

Abstract

Background

Few studies report the effectiveness of trivalent inactivated influenza vaccine (TIV) in preventing hospitalisation for influenza-confirmed respiratory infections. Using a prospective surveillance platform, this study reports the first such estimate from a well-defined ethnically diverse population in New Zealand (NZ).

Methods

A case test-negative design was used to estimate propensity adjusted vaccine effectiveness. Patients with a severe acute respiratory infection (SARI), defined as a patient of any age requiring hospitalisation with a history of a fever or a measured temperature ≥38 °C and cough and onset within the past 7 days, admitted to public hospitals in South and Central Auckland were eligible for inclusion in the study. Cases were SARI patients who tested positive for influenza, while non-cases (controls) were SARI patients who tested negative. Results were adjusted for the propensity to be vaccinated and the timing of the influenza season.

Results

The propensity and season adjusted vaccine effectiveness (VE) was estimated as 39% (95% CI 16;56). The VE point estimate against influenza A (H1N1) was lower than for influenza B or influenza A (H3N2) but confidence intervals were wide and overlapping. Estimated VE was 59% (95% CI 26;77) in patients aged 45–64 years but only 8% (−78;53) in those aged 65 years and above.

Conclusion

Prospective surveillance for SARI has been successfully established in NZ. This study for the first year, the 2012 influenza season, has shown low to moderate protection by TIV against influenza positive hospitalisation.

Introduction

Influenza continues to cause a significant burden of illness in adults and children [1], [2] despite vaccines having been used internationally for more than 60 years and being recommended by the World Health Organization [3]. Estimates of efficacy (from trials) and effectiveness (from observational studies) for seasonal trivalent inactivated vaccine (TIV) have been variable. An umbrella review of meta-analyses of community studies from 2005 to 2011 concluded that protection against laboratory-confirmed influenza (largely mild disease) by TIV ranged from 59 to 65% with estimates being similar in working age adults and children aged 2 years and above [4]. There have been too few trials in children under 2 years for accurate estimates of efficacy in this age group [5], [6]. Observational studies provide a range of effectiveness estimates from zero to approximately 60% protection in young children [7], [8]. While studies specifically of older adults are less common, vaccine effectiveness (VE) has been reported to be as high as 57% in adults over 70 years [6], there are significant concerns over bias in studies in this age group [9] and other studies report much lower or even null estimates [10]. However significant variability by season is acknowledged [6] and increasing immunosenescence and the presence of comorbidities are likely to reduce effectiveness [6].

Results are more limited when reviewing protection against influenza-confirmed hospitalisation. No trials address this outcome. Estimates from observational studies include no protection by TIV against laboratory-confirmed influenza [11] to a protective range of 49% to 61% in adults [12], [13], [14]. Pooled European data for VE against A (H3N2) during 2011/2012 gave a point estimate for the target groups for vaccination of 29% with wide confidence intervals [15].

The antigenic composition of influenza vaccines is reviewed annually to predict the best match for a constantly evolving virus. The impact of vaccination is expected to be higher in the presence of a good antigenic match, although significant effectiveness has been shown even in seasons when the circulating strain is not a good match [16], [17].

In New Zealand (NZ) seasonal unadjuvanted TIV is offered annually free of charge to all adults aged 65 years and over, pregnant women and all those over 6 months of age with chronic medical conditions that are likely to increase severity of infection. The vaccines are also available from early March on the private market for all others over 6 months of age. The influenza season usually occurs somewhere between early May and late September.

Using a case test-negative design (a modification to the case-control study design [18]), we aimed to estimate the effectiveness of seasonal TIVs in preventing hospitalised laboratory-confirmed influenza in persons aged at least 6 months who were admitted with an acute respiratory illness to public hospitals in Central, South and East Auckland between April 2012 and February 2013. The study reports results from the first year of a five year SHIVERS (Southern Hemisphere Influenza Vaccine Effectiveness, Research and Surveillance) project.

Section snippets

Methods

Ethics approval for the study was obtained from the Northern A Health and Disability Ethics Committee (NTX/11/11/102 AM02).

Study design

We used the standard case test-negative design [19] and a similar analytic approach to a previous study of hospitalised patients, with adjustment for the propensity to be vaccinated [13]. From 30 April 2012 to 28th February 2013 we attempted to enrol all individuals aged 6 months and older who were hospitalised with a severe acute respiratory infection (SARI). Based on the World Health Organization definition, this was defined as a patient requiring hospitalisation with a patient-reported

Participant information

Demographic data collected for all cases and non-cases included age; sex; ethnicity (Māori, Pacific, Asian, NZ European or other); and income, with low income defined as a household that received either a government benefit or held a community services card. The age data were cross validated with hospital held electronic data. Clinical information was obtained from both the case report form and electronic data extraction from hospital databases. These data included clinical symptoms and signs;

Laboratory methods

Nasopharyngeal swabs were collected with a COPAN flocked swab and transported in viral transport medium (VTM) at 4 °C. Nasopharyngeal aspirates and other respiratory samples were collected according to hospital standard operational procedures. Respiratory samples were tested using the United States Center for Disease Control and Prevention real time RT-PCR protocol [22] at Auckland District Health Board Laboratory and the AusDiagnostic PCR protocol at the Counties Manukau District Health Board

Statistical analysis

The influenza season was defined to start when there were two consecutive weeks of four or more cases and to end when there were no consecutive weeks of four or more cases. Patients at higher risk of an adverse outcome from influenza infection, and for whom the vaccine is provided at no charge, may be more likely to be vaccinated. We allowed for this by using a multivariate logistic model to calculate the propensity to get vaccinated for the controls, given the range of available patient

Results

The influenza season ran from the 28th of May 2012 until the 10th of October 2012. Case selection and exclusion/inclusion criteria are shown in Fig. 1. Of the 6373 admissions screened, 2682 (42%) met the definition of SARI. After exclusions for lack of consent (n = 224), no record of vaccination history (n = 300), no recorded date of birth (n = 1), aged less than 6 months (n = 226), outside of influenza season (n = 484) or no laboratory results available (n = 88), a total of 1359 admissions remained, of

Vaccine effectiveness

The VE against any influenza infection and adjusted only for the timing relative to the peak of season was 27% (95% confidence interval 6;44). After adjusting for the propensity to be vaccinated the estimated VE was 39% (16;56). In the sensitivity analysis, the VE against any influenza infection estimated from the epidemiological model was 42% (19;58) and from the statistical model was 41% (21;58). There was no significant change to these estimates when omitting patients with missing values or

Discussion

This study has four important findings. First, we found that 21% of SARI admissions in Auckland during the study period were due to influenza. Second, VE against hospitalisation for the 2012 season was relatively low with a point estimate of 39%. Third, while underpowered to show age effects, vaccination appeared less effective in patients aged at least 65 years although this finding may reflect response to the circulating influenza type rather than an age effect, and lastly VE varied by

Strengths and limitations

The strengths of this study include the establishment of an effective influenza surveillance system in New Zealand, and using RT-PCR-confirmed hospitalised influenza as the outcome measure. Estimating VE against the severe outcome of hospitalisation may have more relevance for public health policy than estimation of protection against mild disease that is managed in the community. The recruitment process selected potential SARI cases from a full range of respiratory illness categories including

Acknowledgements

The SHIVERS (Southern Hemisphere Influenza and Vaccine Effectiveness Research and Surveillance) project is funded by U.S. Department of Health and Human Services, Centers for Disease Control and Prevention (CDC) (1U01IP000480-01). The SARI surveillance is a key component of the SHIVERS project. The project is a five year research cooperative agreement between Institute of Environmental Science and Research and US CDC's National Center for Immunization and Respiratory Diseases (NCIRD) Influenza

References (31)

H. Nair
Global burden of respiratory infections due to seasonal influenza in young children: a systematic review and meta-analysis
Lancet
(2011)
J. Puig-Barbera
Effectiveness of seasonal 2009–2009, 2009–2010 and pandemic vaccines, to prevent influenza hospitalizations during the autumn 2009 influenza pnademic wave in Castellon, Spain. A test-negative, hospital-based, case-control study
Vaccine
(2010)
A.C. Cheng
Effectiveness of H1N1/09 monovalent and trivalent influenza vaccines against hospitalization with laboratory-confirmed H1N1/09 influenza in Australia: a test-negative case control
Vaccine
(2011)
I.M. Foppa
The case test-negative design for studies of the effectiveness of influenza vaccine
Vaccine
(2013)
R. Baxter et al.
Effect of influenza vaccination on hospitalizations in persons aged 50 years and older
Vaccine
(2010)
S.A. Skull
Validity of self-reported influenza and pneumococcal vaccination status among a cohort of hospitalized elderly inpatients
Vaccine
(2007)
F. Carrat
Influenza burden of illness: estimates from a national prospective survey of household contacts in France
Arch Intern Med
(2002)
World Health Organization
WHO vaccine use
(2013)
L. Manzoli
Effectiveness and harms of seasonal and pandemic influenza vaccines in children, adults and elderly: a critical review and re-analysis of 15 meta-analyses
Hum Vaccine Immunother
(2012)
T. Jefferson
Vaccines for preventing influenza in healthy children
Cochrane Database Syst Rev
(2008)

M.T. Osterholm

Efficacy and effectiveness of influenza vaccines: a systematic review and metaanalysis

Lancet Infect Dis

(2011)

A. Hoberman

Effectiveness of inactivated influenza vaccine in preventing acute otitis media in young children: a randomized controlled trial

JAMA

(2003)

C.M. Shuler

Vaccine effectiveness against medically attended: laboratory-confirmed influenza among children aged 6 to 59 months, 2003–2004

Pediatrics

(2007)

R. Baxter et al.

Evidence of bias in studies of influenza vaccine effectiveness in elderly patients

J Infect Dis

(2010)

T. Jefferson

Vaccines for preventing inﬂuenza in the elderly

Cochrane Database of Systematic Reviews

(2010)

Cited by (29)

Influenza vaccine effectiveness against influenza-associated hospitalization in children: A systematic review and meta-analysis
2020, Vaccine
Citation Excerpt :
When we further sub-grouped by age, influenza VE against hospitalization was 54.40% (95% CI: 33.37–75.43) in children 6 months to 2 years old (Fig. 6), and 73.14% (95% CI: 67.53–78.76) in children 2–5 years old (Fig. 6). Also, based on 5 studies [22,25–27,38], influenza VE against hospitalization in children 6–17 years was 54.37% (95% CI: 35.14–73.60) (Fig. S2). We utilized the Newcastle-Ottawa scale to assess included studies quality.
Vaccination remains the most effective way to prevent influenza infection, albeit vaccine effectiveness (VE) varies by year. Compared to other age groups, children and elderly adults have the highest risk of developing influenza-related complications and requiring hospitalization. During the last years, “test negative design” (TND) studies have been implemented in order to estimate influenza VE. The aim of this systematic review and meta-analysis was to summarize the findings of TND studies reporting influenza VE against laboratory-confirmed influenza-related hospitalization in children aged 6 months to 17 years. We searched the PubMed and Embase databases and identified 2615 non-duplicate studies that required detailed review. Among them, 28 met our inclusion criteria and we performed a random-effects meta-analysis using adjusted VE estimates. In our primary analysis, influenza vaccine offered significant protection against any type influenza-related hospitalization (57.48%; 95% CI 49.46–65.49). When we examined influenza VE per type and strain, VE was higher against H1N1 (74.07%; 95% CI: 54.85–93.30) and influenza B (50.87%; 95% CI: 41.75–59.98), and moderate against H3N2 (40.77%; 95% CI: 25.65–55.89). Notably, influenza vaccination offered higher protection in children who were fully vaccinated (61.79%; 95% CI: 54.45–69.13), compared to those who were partially vaccinated (33.91%; 95% CI: 21.12 – 46.69). Also, influenza VE was high in children less than 5 years old (61.71%; 95% CI: 49.29–74.12) as well as in children 6–17 years old (54.37%; 95% CI: 35.14–73.60). In conclusion, in the pediatric population, influenza vaccination offered significant protection against influenza-related hospitalization and complete annual vaccination should be encouraged.
Influenza vaccine effectiveness in preventing influenza-associated intensive care admissions and attenuating severe disease among adults in New Zealand 2012–2015
2018, Vaccine
Citation Excerpt :
Although the TND minimizes biases associated with access to IIV3 and healthcare seeking for ARI [18,19], additional adjustments may be needed in studies examining IVE or predictors of disease severity in hospital settings [20,21]. Thus, SHIVERS [6,7] and other studies of IVE in hospital settings [22,23] have employed propensity score regression adjustment to reduce residual confounding [24]. The propensity score is the inverse logit transformation of the linear predictor derived from multivariable logistic regression as a function of the socio-demographic, chronic medical conditions, and other health status variables (listed in full in Supplemental Table A).
Little is known about inactivated influenza vaccine effectiveness (IVE) in preventing very severe disease, including influenza-associated intensive care unit (ICU) admissions.
The Southern Hemisphere Influenza and Vaccine Effectiveness Research and Surveillance (SHIVERS) project enrolled adults (aged ≥ 18 years) with acute respiratory illness (ARI) in general ward (GW) hospital settings (n = 3034) and ICUs (n = 101) during 2012–2015. IVE was assessed using a test-negative design comparing the odds of influenza vaccination among influenza positives vs. negatives (confirmed by real-time reverse transcription polymerase chain reaction). All models were adjusted for season, weeks from season peak, and a vaccination propensity score.
Influenza virus infection was confirmed in 28% of GW hospital and 41% of ICU patients; influenza vaccination was documented for 56% and 41%, respectively. Across seasons, IVE was 37% (95% confidence intervals [CI] = 23–48%) among GW patients and 82% (95% CI = 45–94%) among ICU patients. IVE point estimates were > 70% against ICU influenza and consistently higher than IVE against GW influenza when stratified by season, by virus (sub)types, and for adults with or without chronic medical conditions and for both adults aged <65 and ≥65 years old. Among hospitalized influenza positives, influenza vaccination was associated with a 59% reduction in the odds of ICU admission (aOR = 0.41, 95% CI = 0.18–0.96) and with shorter ICU lengths of stay (LOS), but not with radiograph-confirmed pneumonia or GW hospital LOS.
Inactivated influenza vaccines prevented influenza-associated ICU admissions, may have higher effectiveness in ICU than GW hospital settings, and appeared to reduce the risk of severe disease among those who are infected despite vaccination.
Effectiveness of influenza vaccination for children in Japan: Four-year observational study using a large-scale claims database
2018, Vaccine
To date, few large-scale comparative effectiveness studies of influenza vaccination have been conducted in Japan, since marketing authorization for influenza vaccines in Japan has been granted based only on the results of seroconversion and safety in small-sized populations in clinical trial phases not on the vaccine effectiveness. We evaluated the clinical effectiveness of influenza vaccination for children aged 1–15 years in Japan throughout four influenza seasons from 2010 to 2014 in the real world setting.
We conducted a cohort study using a large-scale claims database for employee health care insurance plans covering more than 3 million people, including enrollees and their dependents. Vaccination status was identified using plan records for the influenza vaccination subsidies.
The effectiveness of influenza vaccination in preventing influenza and its complications was evaluated. To control confounding related to influenza vaccination, odds ratios (OR) were calculated by applying a doubly robust method using the propensity score for vaccination.
Total study population throughout the four consecutive influenza seasons was over 116,000. Vaccination rate was higher in younger children and in the recent influenza seasons. Throughout the four seasons, the estimated ORs for influenza onset were statistically significant and ranged from 0.797 to 0.894 after doubly robust adjustment. On age stratification, significant ORs were observed in younger children. Additionally, ORs for influenza complication outcomes, such as pneumonia, hospitalization with influenza and respiratory tract diseases, were significantly reduced, except for hospitalization with influenza in the 2010/2011 and 2012/2013 seasons.
We confirmed the clinical effectiveness of influenza vaccination in children aged 1–15 years from the 2010/2011 to 2013/2014 influenza seasons. Influenza vaccine significantly prevented the onset of influenza and was effective in reducing its secondary complications.
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)
2018, Vaccine
Citation Excerpt :
Public messaging around the benefits of receiving an influenza vaccination, especially for those individuals at increased risk of influenza virus infection and associated complications, occurs each influenza season [1]. However, recent influenza seasons in Canada (and globally) have been marked by low and variable influenza vaccine effectiveness (VE) as observed by sentinel influenza surveillance networks examining medically-attended influenza in both outpatient and inpatient settings [2–8]. In light of this data, and controversy over the potential negative impact of repeated influenza vaccination [9], this public health message has become diluted.
Ongoing 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.
The 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.
Overall, 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%).
While 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.
Effectiveness of influenza vaccines in preventing severe influenza illness among adults: A systematic review and meta-analysis of test-negative design case-control studies
2017, Journal of Infection
Citation Excerpt :
Repeat influenza vaccination over multiple years has been associated with decreased clinical IVE against influenza A(H3N2) and B viruses associated medical visits.84 Given that documenting current year influenza vaccination status is especially challenging in hospital settings,32,33 it is not surprising that the effect of prior vaccination on IVE was reported in very few articles.36,41,58 Nonetheless, research that considers the possible modification of current season IVE by prior vaccination history among hospitalized patients is needed, especially when consecutive identical vaccine components are followed by an antigenically distinct circulating strain.
Summary evidence of influenza vaccine effectiveness (IVE) against hospitalized influenza is lacking. We conducted a meta-analysis of studies reporting IVE against laboratory-confirmed hospitalized influenza among adults.
We searched Pubmed (January 2009 to November 2016) for studies that used test-negative design (TND) to enrol patients hospitalized with influenza-associated conditions. Two independent authors selected relevant articles. We calculated pooled IVE against any and (sub)type specific influenza among all adults, and stratified by age group (18–64 and 65 years and above) using random-effects models.
We identified 3411 publications and 30 met our inclusion criteria. Between 2010–11 and 2014–15, the pooled seasonal IVE was 41% (95%CI:34;48) for any influenza (51% (95%CI:44;58) among people aged 18–64y and 37% (95%CI:30;44) among ≥65 years). IVE was 48% (95%CI:37;59),37% (95%CI:24;50) and 38% (95%CI:23;53) against influenza A(H1N1)pdm09, A(H3N2) and B, respectively.
Among persons aged ≥65 year, IVE against A(H3N2) was 43% (95%CI:33;53) in seasons when circulating and vaccine strains were antigenically similar and 14% (95%CI:-3;30) when A(H3N2) variant viruses predominated.
Influenza vaccines provided moderate protection against influenza-associated hospitalizations among adults. They seemed to provide low protection among elderly in seasons where vaccine and circulating A(H3N2) strains were antigenically variant.
Effectiveness of seasonal influenza vaccination in community-dwelling elderly people: an individual participant data meta-analysis of test-negative design case-control studies
2017, The Lancet Respiratory Medicine
Several aggregate data meta-analyses have provided estimates of the effectiveness of influenza vaccination in community-dwelling elderly people. However, these studies ignored the effects of patient-level confounders such as sex, age, and chronic diseases that could bias effectiveness estimates. We aimed to assess the confounder-adjusted effectiveness of influenza vaccines on laboratory-confirmed influenza among elderly people by conducting a global individual participant data meta-analysis.
In this individual participant data meta-analysis, we considered studies included in a previously conducted aggregate data meta-analysis that included test-negative design case-control studies published up to July 13, 2014. We contacted all authors of the included studies on Dec 1, 2014, to request individual participant data. Patients were excluded if their unique identifier was missing, their vaccination status was unknown, their outcome status was unknown, or they had had suspected influenza infection more than once in the same influenza season. Cases were patients with influenza-like illness symptoms who tested positive for at least one of A H1N1, A H1N1 pdm09, A H3N2, or B viruses; controls were patients with influenza-like illness symptoms who tested negative for these virus types or subtypes. Influenza vaccine effectiveness against overall and subtype-specific laboratory-confirmed influenza were the primary and secondary outcomes. We used a generalised linear mixed model to calculate adjusted vaccine effectiveness according to vaccine match to the circulating strains of influenza virus and intensity of the virus activity (epidemic or non-epidemic). Vaccine effectiveness was defined as the relative reduction in risk of laboratory-confirmed influenza in vaccinated patients compared with unvaccinated patients. We did subgroup analyses to estimate vaccine effectiveness according to hemisphere, age category, and health status.
We received 23 of the 53 datasets included in the aggregate data meta-analysis. Furthermore, six additional datasets were provided by data collaborators, which resulted in individual participant data for a total of 5210 participants. A total of 4975 patients had the required data for analysis. Of these, 3146 (63%) were controls and 1829 (37%) were cases. Influenza vaccination was significantly effective during epidemic seasons irrespective of vaccine match status (matched adjusted vaccine effectiveness 44·38%, 95% CI 22·63–60·01; mismatched adjusted vaccine effectiveness 20·00%, 95% CI 3·46–33·68; analyses in the imputed dataset). Seasonal influenza vaccination did not show significant effectiveness during non-epidemic seasons. We found substantial variation in vaccine effectiveness across virus types and subtypes, with the highest estimate for A H1N1 pdm09 (53·19%, 10·25–75·58) and the lowest estimate for B virus types (−1·52%, −39·58 to 26·16). Although we observed no significant differences between subgroups in each category (hemisphere, age, and health status), influenza vaccination showed a protective effect among elderly people with cardiovascular disease, lung disease, or aged 75 years and younger.
Influenza vaccination is moderately effective against laboratory-confirmed influenza in elderly people during epidemic seasons. More research is needed to investigate factors affecting vaccine protection (eg, brand-specific or type-specific vaccine effectiveness and repeated annual vaccination) in elderly people.
University Medical Center Groningen.

View all citing articles on Scopus

¹: Authors in the SHIVERS investigation team: Don Bandaranayake, Jazmin Duque, Cameron C. Grant, Diane Gross, Lyndsay LeComte, Graham Mackereth, Colin McArthur, Sarah Radke, Sally Roberts, Ruth Seeds, Susan Taylor, Paul Thomas, Mark Thompson, Adrian Trenholme, Richard Webby, Deborah A. Williamson, Conroy Wong, Tim Wood.

View full text

The effectiveness of seasonal trivalent inactivated influenza vaccine in preventing laboratory confirmed influenza hospitalisations in Auckland, New Zealand in 2012

Highlights

Abstract

Background

Methods

Results

Conclusion

Introduction

Section snippets

Methods

Study design

Participant information

Laboratory methods

Statistical analysis

Results

Vaccine effectiveness

Discussion

Strengths and limitations

Acknowledgements

Lancet

Vaccine

Vaccine

Vaccine

Vaccine

Vaccine

Influenza burden of illness: estimates from a national prospective survey of household contacts in France

Arch Intern Med

WHO vaccine use

Effectiveness and harms of seasonal and pandemic influenza vaccines in children, adults and elderly: a critical review and re-analysis of 15 meta-analyses

Hum Vaccine Immunother

Vaccines for preventing influenza in healthy children

Cochrane Database Syst Rev

Efficacy and effectiveness of influenza vaccines: a systematic review and metaanalysis

Lancet Infect Dis

Effectiveness of inactivated influenza vaccine in preventing acute otitis media in young children: a randomized controlled trial

JAMA

Vaccine effectiveness against medically attended: laboratory-confirmed influenza among children aged 6 to 59 months, 2003–2004

Pediatrics

Evidence of bias in studies of influenza vaccine effectiveness in elderly patients

J Infect Dis

Vaccines for preventing inﬂuenza in the elderly

Cochrane Database of Systematic Reviews