Health Protection and Influenza Research
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PRIDE Study: Post-pandemic Review of anti-Influenza Drug Effectiveness


Accumulating epidemiological studies indicate that early treatment with antiviral drugs may have reduced the likelihood of hospitalisation, severe outcomes and death. However, these studies are often too small and lack statistical power to produce conclusive findings.

Therefore this study aims to combine and analyse data from many observational studies (case series, case-control and cohort studies) and randomised control trials to provide a reliable assessment of the impact of antiviral use on public health outcomes for the 2009/10 A(H1N1)pdm09 influenza pandemic.

It is hoped that the findings from this study will inform future public health policy for pandemic deployment of antivirals and elucidate the advantages gained during 2009-10. 

Meet the team

Professor Jonathan Nguyen van-Tam
Chair of the Health Protection and Influenza Research Group

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Prof. Van-Tam is a widely recognised national and international expert on influenza and advises multiple governments and the WHO and European Centre for Disease Prevention and Control. He is providing overall strategic leadership of the PRIDE study group.

Dr Puja Myles
Associate Professor of Health Protection and Epidemiology at the University of Nottingham

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Dr Myles’s main area of interest is infectious disease epidemiology. Her current research area is influenza, in particular pandemic influenza. She is the principal investigator of the PRIDE study group.

Dr Jo Leonardi-Bee
Associate Professor in Medical Statistics

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Dr Leonardi-Bee's main areas of research are the applications of systematic reviews and meta-analysis in the epidemiological studies. She is currently involved in a number of trials and projects in the areas of tobacco control, dermatology and is the methodological lead in the PRIDE study group.
Dr Stella Muthuri
Postdoctoral Researcher in Epidemiology

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Dr Muthuri’s current research is a systematic review and individual patient meta-analysis on the impact of antiviral use on public health outcomes for 2009 pandemic influenza A/H1N1. She is involved in the day-to-day running of the PRIDE study.

Dr Sudhir Venkatesan
Research Associate

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Dr Venkatesan obtained a Master’s degree in Public Health from the University of Nottingham in 2011. He is assisting Dr Muthuri with the data standardisation and analysis on the PRIDE study.


See all contact details for HPIRG members


A patient-level global meta-analysis on the effectiveness of antiviral use on outcomes of public health importance during the 2009/10 A(H1N1)pdm09 influenza pandemic.


Findings from IPD meta-analysis investigating the association between neuraminidase inhibitors treatment and mortality have now been published:

Preliminary findings on pneumonia and length of stay as presented at the Fifth European Scientific Working Group on Influenza (ESWI) Conference, Riga, 17th September 2015.

Frequently asked questions

What is the PRIDE Study research collaboration?

We invited institutions worldwide to contribute data that would allow us to investigate the impact of antiviral (neuraminidase inhibitor) use on patient outcomes (severe illness, complications and mortality) of A(H1N1)pdm09 pandemic influenza virus infection.

We have received 81 datasets from 38 countries with a total sample size of 170,858 influenza patients. We have just completed the individual patient data (IPD) meta-analysis investigating the association between neuraminidase inhibitor antivirals and A(H1N1)pdm09 related mortality in the pooled dataset.

A manuscript reporting these findings was accepted for publication following peer review by The Lancet Respiratory Medicine on 18 February 2014 . 

The article along with the  commentary can be found on The Lancet Respiratory Medicine’s website.

View a  word-processed copy of the published manuscript.


Can I view the protocol?

The study protocol was registered with the PROSPERO register of systematic reviews (registration number: CRD42011001273) and can be viewed at:

Who owns the PRIDE Study data?

Although the PRIDE study pooled dataset is being held securely within The University of Nottingham for the purpose of standardisation and analysis, it is the property of individual research groups and as such data will not be disclosed to any third party.

Once we have published all the findings of the IPD analysis, all PRIDE study collaborators will discuss whether they would be happy to allow other researchers (both within and outside the collaboration) to validate our findings on request and under a data sharing agreement.

Please bear in mind that all PRIDE collaborators will need to agree for sharing of the anonymised pooled dataset to take place for the sole purpose of verifying the analyses conducted in Nottingham (not for the purposes of secondary research); and this will be subject to approval from individual institutional review boards.

Once all analyses related to the effectiveness of antivirals have been completed, all PRIDE collaborators will be invited to discuss whether they would be happy to allow the cnsortium to undertake secondary analyses (for example, exploring the effectiveness of antibiotics and corticosteroids).


Will findings from this study be published in a peer-reviewed journal?

We intend to publish all results from this study in peer-reviewed journals. The responsibility for data analysis and preparation of manuscripts lies with the Health Protection and Influenza Research Group at the University of Nottingham.

Draft manuscripts and appropriate supplementary material have been/will always be circulated widely to all authors (including data contributors) for comment/agreement before submission to a peer reviewed journal. Authorship for contributors of individual datasets will be as part of the PRIDE study consortium.

Two investigators from each participating institution are included within the PRIDE study consortium as authors on any publication arising from the consortium. With regard to individual named authorship, ultimately we have to adhere to the rulings and adjudications of individual journals.

We have already conducted a systematic review of published studies on this topic, which has been published in the Journal of Infectious Diseases. Our key finding was that early antiviral use was associated with a significant reduction in mortality compared to late or no antiviral use.


Our primary analysis based an Individual Participant Data (IPD) pooled approach also found that NAI treatment was associated with a reduction in mortality in adult patients hospitalised with influenza A(H1N1)pdm09.



What protocol will be followed when ascribing order of authorship on any publications based on this work?

Due to the potentially large number of willing collaborators (so far we have about 60 interested groups), the study's authorship will be presented as follows: Muthuri, Leonardi-Bee, Venkatesan, Van-Tam, Myles on behalf of the PRIDE study group and name all authors in the PRIDE Study group either as a footnote or before acknowledgments (following journal protocols). This is in keeping with the existing practice for large collaborative meta-analysis and IPD analysis projects.


Will the pooled anonymised dataset be made available to other researchers within the collaboration for validation?

Analysis plans, results and draft manuscripts have been and will be shared with all PRIDE consortium members but at this stage only the Health Protection and Influenza Research Group, University of Nottingham have access to the pooled anonymised dataset.

Ideally, in the spirit of transparency, we would have a publicly accessible pooled dataset so that other researchers can validate our analyses. In reality though, we may not be given permission by individual research groups within the PRIDE consortium or their local ethics boards to share this data even in a pooled format.

We will revisit this discussion with all our collaborators once we have completed all our planned analyses


What is the approximate timeline for the individual patient data meta-analysis?

The first manuscript from this collaborative work ‘Effectiveness of neuraminidase inhibitors in reducing mortality in hospitalised influenza A(H1N1)pdm09 patients: an individual participant data meta-analysis was recently published in the Lancet Respiratory Medicine.

We have also completed analyses relating to the outcomes ‘admission to critical care’, ‘influenza A(H1N1)pdm09 pneumonia’ and ‘length of hospital stay’, and have embarked on analyses relating to the association between antiviral use in the community and admission to hospital. These findings have been/will be presented at various influenza conferences and are being written up for publication.


Who is funding this project?

The study is taking place through an unrestricted educational grant funding from F. Hoffmann-La Roche but is being undertaken fully independently of the company, which has had/will have: no input to the project design; no access to any of the data; no role in analysis or data interpretation; no preview of the study results; and no opportunity to preview or comment on any manuscripts arising from the work.

View the ROCHE contract/letter of clarification 


Can I still contribute my data towards the PRIDE study?

We are no longer actively recruiting new collaborators and the analyses relating to the outcome ‘mortality’,  admission to critical care’, ‘influenza A(H1N1)pdm09 pneumonia’ and ‘length of hospital stay’ have now been completed. We have also started the analyses relating to ‘admission to hospital’ and will have preliminary findings by spring 2014. However, if you are interested in future research collaborations of this nature please do not hesitate to contact one of us:,,




Dr Stella Muthuri
Division of Epidemiology and Public Health
University of Nottingham
Clinical Sciences Building
City Hospital
Hucknall Road
Nottingham, NG5 1PB 

telephone: +44 (0)115 823 1668


Health Protection and Influenza Research

Division of Epidemiology and Public Health
Nottingham City Hospital
The University of Nottingham
Hucknall Road, Nottingham, NG5 1PB

telephone: +44 (0)115 823 0276