Study casts doubt on Tamiflu value
New Zealand will maintain its $32 million stockpile of influenza medicine Tamiflu, despite a major international study throwing doubt on the value of the treatment.
An updated review published by The Cochrane Collaboration, an independent global healthcare research network, and the BMJ said Tamiflu shortened the symptoms of influenza by half a day. There was no good evidence to support claims it reduced admissions to hospital or complications of influenza.
"Along with the evidence of harms from the medication, it raises the question of whether global stockpiling of the drugs is still justifiable given the lack of reliable evidence to support the original claims of its benefits," Cochrane said.
Medicines safety authority Medsafe said this country had a periodically refreshed stockpile of slightly more than 1 million doses of Tamiflu and more than 300,000 doses of another antiviral, Relenza. The Tamiflu stockpile was worth about $32m, out of a national pandemic stockpile, including items such as masks and syringes, worth about $46m.
"This study alone is not sufficient for New Zealand to be reconsidering its position of maintaining stockpiles of Tamiflu as an important precaution in case of a future global influenza pandemic," Medsafe general manager Dr Stewart Jessamine said.
About 100 countries had stockpiles of Tamiflu and Relenza, which was in line with World Health Organisation advice.
Regulators had to consider the widest possible range of research and information, and the Cochrane study had to be placed in that context, Jessamine said.
Another recent study showed clear benefits from the use of Tamiflu. It had looked at the use of Tamiflu in patients with influenza, as opposed to the clinical controlled trials in the Cochrane study.
"Maintaining a Tamiflu stockpile is international best practice. New Zealand will continue to monitor literature on this subject and the considerations of other regulators."
Tamiflu manufacturer Roche rejected Cochrane's findings saying it "fundamentally disagrees with the overall conclusions" of the study.
"We firmly stand by the quality and integrity of our data, reflected in decisions reached by 100 regulators across the world and subsequent real-world evidence demonstrating that Tamiflu is an effective medicine in the treatment and prevention of influenza," it said in a statement reported by Reuters.
The Cochrane finding was based on full internal reports of 20 Tamiflu and 26 Relenza trials. The medicines are both neuraminidase inhibitors used to treat and prevent influenza in healthy adults and children.
Tamiflu was stockpiled around the world during the 2009 swine flu pandemic. Forty-nine New Zealanders died from swine flu that year. Most of them were aged under 60.
Responding to the report, Dr Vanessa Jordan, the New Zealand Cochrane Fellow at the University of Auckland, said available data in 2009 had suggested antivirals such as Tamiflu and Relenza had potential benefits in reducing complications from influenza.
Based on that the Government - following the lead of overseas counterparts - bought and stockpiled 750,000 doses. Most of those doses had since been dumped after passing their expiration date.
The information had been incomplete. Through perseverance the Cochrane authoring group had obtained information on unpublished trials. The new synthesised evidence confirmed what had previously been suspected - "that there is currently no support for claims that Tamiflu or Relenza reduces admissions to hospital or complications of influenza," Jordan said.
"As a result of this latest Cochrane review we can see that there is not a case for widespread use of antivirals for influenza."
Pharmaceutical companies should be required to publish all the data related to effectiveness and safety, Jordan said.
Dr John Cameron, clinical director of Auckland region GP network ProCare Health, said the report raised significant questions about the benefit from either patient or government-funded stocks of neuraminidase inhibitors.
The data would allow planners to look at more effective management strategies such as the greater effectiveness of public health processes, infection control programmes and the early development and delivery of potentially more effective vaccine agents in the management of an influenza pandemic.
"At least now we should be able to reduce the potentially wasteful use of health resources on medications that have not shown to have significant beneficial effects for sufferers of current influenza viruses," Cameron said.
It was not a question of if but when a novel pandemic influenza virus, such as the one that caused the 1918 pandemic, would arise.
As well as questioning the usefulness of Tamiflu, the Cochrane report said the medicine increased the risk of nausea and vomiting in adults by about 4 per cent and in children by 5 per cent.
There was a reported increased risk of psychiatric events of about 1 per cent when Tamiflu was used to prevent influenza.
Evidence also suggested Tamiflu prevented some people producing sufficient numbers of their own antibodies to fight infection.
BMJ editor-in-chief Dr Fiona Godlee said the review was the result of many years of struggles to access and use trial data, which was previously unpublished and even hidden from view.
"We need the full data from clinical trials made available for all drugs in current use," Goodlee said.