Effectiveness of seasonal influenza vaccine in Australia, 2015: An epidemiological, antigenic and phylogenetic assessment

doi:10.1016/j.vaccine.2016.08.067

Vaccine

Volume 34, Issue 41, 22 September 2016, Pages 4905-4912

https://doi.org/10.1016/j.vaccine.2016.08.067 Get rights and content

Highlights

•
Overall, the 2015 inactivated trivalent vaccine was effective against influenza.
•
More widespread use of quadrivalent vaccine could have improved effectiveness.
•
Genetic data indicated mismatch of vaccine and circulating type A(H3) viruses.

Abstract

Background

A record number of laboratory-confirmed influenza cases were notified in Australia in 2015, during which type A(H3) and type B Victoria and Yamagata lineages co-circulated. We estimated effectiveness of the 2015 inactivated seasonal influenza vaccine against specific virus lineages and clades.

Methods

Three sentinel general practitioner networks conduct surveillance for laboratory-confirmed influenza amongst patients presenting with influenza-like illness in Australia. Data from the networks were pooled to estimate vaccine effectiveness (VE) for seasonal trivalent influenza vaccine in Australia in 2015 using the case test-negative study design.

Results

There were 2443 eligible patients included in the study, of which 857 (35%) were influenza-positive. Thirty-three and 19% of controls and cases respectively were reported as vaccinated. Adjusted VE against all influenza was 54% (95% CI: 42, 63). Antigenic characterisation data suggested good match between vaccine and circulating strains of A(H3); however VE for A(H3) was low at 44% (95% CI: 21, 60). Phylogenetic analysis indicated most circulating viruses were from clade 3C.2a, rather than the clade included in the vaccine (3C.3a). VE point estimates were higher against B/Yamagata lineage influenza (71%; 95% CI: 57, 80) than B/Victoria (42%, 95% CI: 13, 61), and in younger people.

Conclusions

Overall seasonal vaccine was protective against influenza infection in Australia in 2015. Higher VE against the B/Yamagata lineage included in the trivalent vaccine suggests that more widespread use of quadrivalent vaccine could have improved overall effectiveness of influenza vaccine. Genetic characterisation suggested lower VE against A(H3) influenza was due to clade mismatch of vaccine and circulating viruses.

Section snippets

Background

Since 2010, the number of notified laboratory confirmed influenza cases in Australia increased by an average of 63% annually to a record 100,582 in 2015 [1]. Notified cases in 2015 were predominantly type B, which was unusual for two reasons. First, there is a widely held belief that seasons dominated by influenza B viruses are mild. However, while this was somewhat reflected in outpatient surveillance data, the large number of notified cases suggested otherwise [2]. Second, influenza seasons

Methods

The Australian Sentinel Practices Research Network (ASPREN), the Victorian Sentinel Practice Influenza Network (VicSPIN), and the Sentinel Practitioners Network of Western Australia (SPNWA) constitute Australia’s three sentinel general practice (GP) networks for influenza surveillance. SPNWA and VicSPIN operate in the respective states of Western Australia and Victoria, whilst ASPREN GPs are primarily located in the other six states and territories, except for several in Victoria.

The sentinel

Participant recruitment

The 354 GPs participating in the three systems conducted 627,381 consultations during the study period, of which 5968 (1%) were reported as meeting the ILI case definition; swabs were collected from 2983 of these ILI patients (50%). Cases of influenza were detected in every week of the study period, with a peak in the number of detections (n = 102) and percent positive (50%) in the weeks ending 9 August (week 31) and 23 August (week 33), respectively (Fig. 1). After exclusion of 540 records

Discussion

The 2015 influenza season in Australia was characterised by the predominance of type B viruses, the first year this has been observed since 2008 [24]. With an overall point estimate of 58%, the vaccine provided moderate protection against type B influenza. Consistent with the composition of the TIV (which we assumed most vaccine recipients received), the VE point estimate was higher against B/Yamagata influenza (71%) than viruses from the B/Victoria lineage (42%). This observation is further

Conflict of interest statement

All authors report that they do not have a commercial or other association that might pose a conflict of interest.

Acknowledgements

We thank the general practitioners that participated and contributed to ASPREN, VicSPIN and SPNWA in 2015. We also thank laboratory staff members from the following laboratories who undertook influenza testing: and virus characterisation: SA Pathology, Adelaide, South Australia; PathWest Laboratory Medicine WA, Perth, Western Australia; the Victorian Infectious Diseases Reference Laboratory, Melbourne, Victoria; and the WHO Collaborating Centre for Reference and Research on Influenza,

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Variable seasonal influenza vaccine effectiveness across geographical regions, age groups and levels of vaccine antigenic similarity with circulating virus strains: A systematic review and meta-analysis of the evidence from test-negative design studies after the 2009/10 influenza pandemic
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The specific age ranges included in each of the a priori determined age categories for pooled VE by age is detailed in Supplementary Table 3. From a total 11,931 identified citations, 76 full-text articles met our eligibility criteria for inclusion (Fig. 1) [15–90]. These articles comprised 13 articles from Spain [18–20,32,33,37–40,46–48,71], 12 articles from the USA [16,23,29–31,36,51,54,65,70,83,90], ten articles from Australia [17,26,27,41–43,67,68,80,81], eight articles from the UK [15,55–61], seven articles from Canada [71–78], four articles from China [45,86,88], three articles from Germany [25,35,52], two articles each from Israel [79,89], Japan [22,82], Netherlands [24,84], Romania [63,64], and South Africa [49,50], and one article each from Austria [66], Croatia [28], France [85], Hong Kong [21], Italy [69], New Zealand [62], Portugal [53], Taiwan [44], and Turkey [34].
We examined the influence of some factors on seasonal influenza vaccine effectiveness (VE) from test-negative design (TND) studies.
We systematically searched for full-text publications of VE against laboratory-confirmed influenza from TND studies in outpatient settings after the 2009/10 influenza pandemic. Two reviewers independently selected and extracted data from the included studies. We calculated pooled adjusted VE across geographical regions, age groups and levels of vaccine antigenic similarity with circulating virus strains, using an inverse variance, random-effects model.
We included 76 full-text articles from 11,931 citations. VE estimates against A(H1N1)pdm09, A(H3N2), influenza B, and all influenza were homogenous and point pooled VE higher in the Southern hemisphere compared with the Northern hemisphere. The difference in pooled VE between the Southern and Northern hemispheres was statistically significant for A(H3N2), influenza B, and all influenza. A consistent pattern was observed in pooled VE across both hemispheres and continents, with the highest point pooled VE being against A(H1N1)pdm09, followed by influenza B, and lowest against A(H3N2). A nearly consistent pattern was observed in pooled VE across age groups in the Northern hemisphere, with pooled VE mostly decreasing with age. Point pooled VE against A(H3N2), influenza B, and all influenza were statistically significantly higher when vaccine was antigenically similar to circulating virus strains compared with when antigenically dissimilar. Similar pattern was observed in the Northern hemisphere, but there was a lack of data from the Southern hemisphere.
Consistent patterns appear to exist in seasonal influenza VE across regions, age groups, and levels of vaccine antigenic similarity with circulating virus strains, with best vaccine performance against A(H1N1)pdm09 and worst against A(H3N2). The evidence highlights the need to consider geographical location, age, and vaccine antigenic similarity with circulating virus strains when designing and evaluating influenza VE studies.
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Data from three sentinel surveillance systems were collected: the Australian Sentinel Practices Research Network (ASPREN), the Sentinel Practitioners Network of Western Australia (SPNWA), and the Victoria Sentinel Practice Influenza Network (VicSPIN). These systems have been described elsewhere [7,8] and in 2016 included 24 general practices in Western Australia (SPNWA), 32 practices in Victoria (VicSPIN), and 97 practices from the remaining states (ASPREN). Sentinel GPs collected information on patients presenting with influenza-like illness (ILI) during the influenza season.
We estimated the effectiveness of seasonal inactivated influenza vaccine and the potential influence of timing of immunization on vaccine effectiveness (VE) using data from the 2016 southern hemisphere influenza season.
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A total of 1085 patients tested for influenza in 2016 were included in the analysis, of whom 447 (41%) tested positive for influenza. The majority of detections were influenza A/H3N2 (74%). One-third (31%) of patients received the 2016 southern hemisphere formulation influenza vaccine. Overall, VE was estimated at 40% (95% CI: 18–56%). VE estimates were highest for patients immunized within two months prior to symptom onset (VE: 60%; 95% CI: 26–78%) and lowest for patients immunized >4 months prior to symptom onset (VE: 19%; 95% CI: −73–62%).
Overall, the 2016 influenza vaccine showed good protection against laboratory-confirmed infection among general practice patients. Results by duration of vaccination suggest a significant decline in effectiveness during the 2016 influenza season, indicating immunization close to influenza season offered optimal protection.
Estimating influenza vaccine effectiveness using data routinely available in electronic primary care records
2019, Vaccine
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In 2013, the eHR system estimated VE to be 57% and published figures from Australia found it was 60% effective [6]. In 2015, the eHR derived VE was estimated to be 50% and published estimates indicated the vaccine was 54% effective [12]. In 2014, however, our eHR system estimated VE to be 60% and published estimates indicated it was 44%, although the 95% confidence interval for our estimate (41–73%) overlaps with those for the published estimate (31–55%) [6].
To support timely, annual estimation of influenza vaccine effectiveness (VE), we explored the use of automated data extraction from general practice records to estimate VE over four consecutive southern hemisphere influenza seasons.
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A total of 7270 influenza PCR test results were identified of which 1907 (26.2%) were positive; 9.4% of patients with a positive result had received contemporaneous influenza vaccination ≥14 days prior to specimen collection, compared to 17.9% of those with a negative result. Overall VE was 52% (95% CI, 43–60%); annual VE estimates ranged from 46% (95% CI, 22–63%) in 2012 to 60% (95% CI, 41–73%) in 2014.
Electronic records routinely maintained by general practice provide a promising opportunity for estimating annual influenza VE in a timely and resource-efficient manner.
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Citation Excerpt :
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Effectiveness of seasonal influenza vaccine in Australia, 2015: An epidemiological, antigenic and phylogenetic assessment

Highlights

Abstract

Background

Methods

Results

Conclusions

Section snippets

Background

Methods

Participant recruitment

Discussion

Conflict of interest statement

Acknowledgements

Vaccine

Vaccine

Vaccine

Virology

Vaccine

J Clin Virol

Vaccine

How severe was the 2015 influenza season in Australia?

Med J Aust

Differential age susceptibility to influenza B/Victoria lineage viruses in the 2015 Australian influenza season

Euro Surveill

The Australian immunisation handbook

Adult vaccination survey

Recommended composition of influenza virus vaccines for use in the 2015 southern hemisphere influenza season

Wkly Epidemiol Rec

Interim estimates of 2014/15 vaccine effectiveness against influenza A(H3N2) from Canada’s sentinel physician surveillance network, January 2015

Euro Surveill

Increased prevalence of influenza B/Victoria lineage viruses during early stages of the 2015 influenza season in New South Wales, Australia: implications for vaccination and planning

Euro Surveill

Recommended composition of influenza virus vaccines for use in the 2015–2016 northern hemisphere influenza season

Wkly Epidemiol Rec

Influenza virus characterisation, summary Europe, December 2015

Pooled influenza vaccine effectiveness estimates for Australia, 2012–2014

Epidemiol Infect

Influenza vaccine effectiveness in Australia: results from the Australian sentinel practices research network

Med J Aust

An economical tandem multiplex real-time PCR technique for the detection of a comprehensive range of respiratory pathogens

Viruses

Evaluation of real-time reverse transcriptase PCR assays for detection of pandemic influenza A/H1N1 2009 virus

J Clin Microbiol