# 5494
The supposed link between GSK’s Pandemrix Vaccine and an increase in narcolepsy among children and adolescents in a handful of countries has been covered often in this blog over the past 6 months.
Today, new we’ve information from the EMA. But first, a quick review of the story to date.
In late August of 2010, shortly after the declared end of the H1N1 pandemic, reports of a possible increase in narcolepsy among children and adolescents who received GSK’s adjuvanted Pandemrix vaccine began to emerge from Finland.
On August 25th, I reported Finland Suspends Use of Pandemrix Vaccine, and two days later I blogged on the European Medicines Agency’s plan to review the evidence (see EMA To Review Pandemrix Vaccine).
Since then we’ve seen several interim reports that failed to find conclusive evidence of a link between the Pandemrix vaccine and narcolepsy, but which did find reasons to continue the investigation.
Sweden: No Link Between Pandemrix And Narcolepsy
EMA Update On The Pandemrix-Narcolepsy Investigation
On February 1st, Finland’s National Institute for Health and Welfare released an interim report on what they called a probable link between GSK’s Pandemrix vaccination, and an increase in narcolepsy in children and adolescents 4-19 years of age.
Finland: Statement On Pandemrix And Narcolepsy Link
A week later, the World Health Organization’s GACVS (Global Advisory Committee on Vaccine Safety) has issued a statement on the potential link between GSK’s Pandemrix vaccine and an increase in rates of narcolepsy among recipients aged 4 to 19.
While stating that further investigation is warranted concerning narcolepsy and vaccination against influenza (H1N1) 2009 with Pandemrix and other pandemic H1N1 vaccines the advisory group also states that this does not appear to have been a world-wide phenomenon.
WHO: GACVS Statement On Narcolepsy And Vaccination
Roughly 10 days later, the European Medicines Agency (EMA) released a statement (see EMA: Added Concern, But Insufficient Evidence To Link Vaccine To Narcolepsy) that stated that that its Committee for Medicinal Products for Human Use (CHMP) has reviewed Finnish data on the suspected link between Pandemrix vaccine and an increase in narcolepsy, and has concluded that the new evidence `added to the concern’, but was as yet insufficient to establish a causal relationship.
Today (April 15th, 2011), in the latest installment in this ongoing investigation, the EMA’s Committee for Medicinal Products for Human Use (CHMP) has recommended that Pandemrix’s product information be amended to include concerns over a suspected link to narcolepsy.
15/04/2011
European Medicines Agency recommends interim measures for Pandemrix
The European Medicines Agency’s Committee for Medicinal Products for Human Use (CHMP) has recommended that the product information for Pandemrix should be amended to advise prescribers to take into account preliminary results from epidemiological studies on Pandemrix and narcolepsy, and to perform an individual benefit-risk assessment when considering the use of Pandemrix in children and adolescents. This is an interim measure pending the outcome of the European review, expected to conclude in July 2011.
The CHMP reviewed all available data, including new findings from Sweden and France on the suspected link between narcolepsy in children and adolescents and Pandemrix. The CHMP concluded that, following the earlier results of an epidemiological study from Finland, the new evidence strengthened the signal in children and adolescents, but that the data had methodological limitations. The relationship between Pandemrix and narcolepsy is still under investigation.
Preliminary results of the Swedish registry study from October 2009 to December 2010 on Pandemrix vaccination and the risk of narcolepsy indicates a four-fold increase of cases of narcolepsy in children and adolescents (below 20 years of age) who received Pandemrix compared with unvaccinated people of the same age. The additional risk corresponds to an additional 3-4 narcolepsy cases per 100,000 vaccinated subjects. These results are broadly in line with the study results from Finland indicating an association between Pandemrix and narcolepsy in children and adolescents. The study did not identify any increased risk in adults. The CHMP concluded that the study was well conducted, although it has inherent limitations.
An analysis of narcolepsy reports in France provides some further evidence.
The lack of a clear increase in reports of narcolepsy following Pandemrix in other EU and non-EU countries may point towards the influence of other unknown factors affecting the trend seen in some countries. Also, there is currently no clearly identified biological plausibility for an association between Pandemrix and narcolepsy, and further non-clinical studies, especially in the juvenile setting, are needed.
The CHMP considers it important to gather more data on the use of Pandemrix and related vaccines in a variety of countries to further assess this concern. A variety of research efforts are now ongoing. These include an epidemiological study of narcolepsy and pandemic vaccines conducted by the European Centre for Disease Prevention and Control (ECDC) through a network of research and public health institutions (VAESCO) in nine European Union Member States, and an epidemiological study conducted by Glaxo Smith Kline (the marketing authorisation holder of Pandemrix) in Canada. Preliminary results of the VAESCO study and of the Canadian study are expected by July 2011.
The CHMP is working with experts from across the EU to assess the possible safety concern and any impact on the benefit-risk balance of Pandemrix. The CHMP plans to hold an expert meeting with participation of international experts, the World Health Organization (WHO) and ECDC.
The European Medicines Agency will provide updates as new information becomes available.
The increase in narcolepsy among children in just a few of the nations that deployed the Pandemrix vaccine remains a medical mystery. Investigations continue.
While some link between the vaccine and the condition may well exist, researchers are looking for a third factor – an unknown catalyst – that may have affected residents of some countries but not others.
The Pandemrix vaccine was not used in the United States.
This is an evolving story, and for now there are more questions than answers.
