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Nearly 11 months ago we began seeing reports of a possible link between narcolepsy in children in a handful of European countries, and the receiving of GSK’s Pandemrix vaccine.
Since then, there have been epidemiological investigations that have confirmed elevated levels of childhood narcolepsy among Pandemrix vaccine recipients in some countries, but not in others.
And that, as you might imagine, has presented public health officials with a bit of a medical mystery.
A few earlier blogs on this subject include:
EMA Recommends Interim Measures For Pandemrix Vaccine
WHO: GACVS Statement On Narcolepsy And Vaccination
Finland: Statement On Pandemrix And Narcolepsy Link
EMA Update On The Pandemrix-Narcolepsy Investigation
Sweden: No Link Between Pandemrix And Narcolepsy
GSK Press Statement On Pandemrix Investigation
The EMA (European Medicines Agency) is a regulatory agency that is responsible for the scientific evaluation of drugs developed by pharmaceutical companies for use in the European Union.
It is roughly the EU equivalent to the United State’s FDA.
Today, in light of their ongoing investigation, they have issued a statement that recommends restricting the use of the Pandemrix vaccine – except under extraordinary circumstances - to only those over the age of 20.
Note: The use of GSK’s 2009 monovalent Pandemrix vaccine has been largely supplanted by the introduction of last year’s trivalent vaccine, so the impact of this ruling should be minimal.
Stockpiles were released last winter in the UK during their surge in flu cases (see UK: To Release Pandemrix Vaccine Stockpile).
The press release (below) provides intriguing glimpses at the avenues under investigation, including genetic predisposition, environmental factors, and perhaps even previous viral exposure as possible catalysts that - along with the vaccine - may have contributed to the increased rates of narcolepsy.
More study will be needed to determine the actual cause or causes.
21/07/2011
European Medicines Agency recommends restricting use of Pandemrix
In persons under 20 years of age Pandemrix to be used only in the absence of seasonal trivalent influenza vaccines, following link to very rare cases of narcolepsy in young people. Overall benefit-risk remains positive.
Finalising its review of Pandemrix and narcolepsy the European Medicines Agency’s Committee for Medicinal Products for Human Use (CHMP) recommended that in persons under 20 years of age Pandemrix may only be used if the recommended seasonal trivalent influenza vaccine is not available and if immunisation against H1N1 is still needed (e.g. in persons at risk of the complications of infection). The CHMP confirmed that overall the benefit-risk balance of Pandemrix remains positive.
The review of Pandemrix was initiated to investigate a possible link between Pandemrix vaccination and narcolepsy, following an increased number of reported cases of narcolepsy among children and adolescents in Finland and Sweden. The reported cases of narcolepsy occurred following the H1N1 pandemic vaccination campaign in late 2009 and early 2010. The current review has been conducted in the context of seasonal use.
The CHMP considered all available data on the possible association between Pandemrix and narcolepsy and the impact on the overall benefit-risk balance of Pandemrix. These included the results of epidemiological studies carried out in Finland and Sweden, analysis of safety surveillance data performed in several Member States and case reports from across the European Union (EU).
They also included the preliminary results of an epidemiological study of narcolepsy and pandemic vaccines in eight EU Member States, coordinated by the European Centre for Disease Prevention and Control (ECDC) through a network of research and public health institutions (VAESCO).
The CHMP also took advice from a specially convened meeting of experts in fields such as paediatric neurology, vaccinology, immunology, sleep disorders, infectious diseases, epidemiology, as well as experts from Health Canada, the World Health Organization (WHO) and the ECDC, to consider the latest available data regarding the possible link between Pandemrix and narcolepsy.
The CHMP considered that the epidemiological studies relating to Pandemrix in Finland and Sweden were well designed and the results show an association between Pandemrix vaccination and narcolepsy in children and adolescents in those countries. The results indicate a six- to 13-fold increased risk of narcolepsy with or without cataplexy in vaccinated as compared with unvaccinated children and adolescents, corresponding to about an additional three to seven cases in every 100,000 vaccinated subjects. This risk increase has not been found in adults (older than 20 years). A similar risk has not been confirmed but cannot be ruled out in other countries.
The Committee noted that the vaccine is likely to have interacted with genetic or environmental factors which might raise the risk of narcolepsy, and that other factors may have contributed to the results. There are several initiatives being developed across the EU to further investigate this association.
The CHMP noted that similar epidemiological studies have not been completed in other countries. The preliminary results of the VAESCO study confirmed the signal in Finland. Results are still preliminary and do not allow conclusions in other countries (where vaccination coverage with Pandemrix was lower), but the final results of the VAESCO study are still awaited.
Exposure to specific infectious diseases (including H1N1) at different ages, particularly upper respiratory infections, may have contributed to the observations in the Nordic area. The CHMP considered that it would be helpful if ongoing epidemiological studies seek to address this question.
The CHMP stressed that further research is necessary.
The Pandemrix vaccine was not used in the United States, although an equivalent H1N1 vaccine (Arepanrix) was widely used in Canada.
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