By Niall Hunter & Sonja Storm
Evidence is growing on a link between the swine flu vaccine Pandemrix and the sleep disorder narcolepsy, with at least 13 cases in Ireland now possibly linked to the vaccine.
New research from Sweden published late last week has strengthened the growing evidence of an association between vaccination with Pandemrix and narcolepsy with cataplexy in children and adolescents. The study showed a greater risk than previously reported of narcolepsy developing in young people who received the Pandemrix vaccine.
Here, the Irish Medicines Board (IMB) has advised any concerned parents to contact their GP for advice on assessment, follow-up and management but it has stressed that a definite causal link between the vaccine and narcolepsy has not been confirmed.
Narcolepsy is a disabling chronic brain disorder characterised by frequent excessive daytime sleepiness. Cataplexy (muscle weakness), sleep paralysis and hallucinations often accompany narcolepsy.
The Irish Medicines Board (IMB) told irishhealth.com it had now received 13 reports with clinical information that confirmed a diagnosis of narcolepsy in individuals vaccinated with Pandemrix, but it said a definitive causal link between the vaccine and the brain condition had not yet been established.
However, the IMB added it was aware that investigations are ongoing on other cases where a diagnosis of narcolepsy was suspected and said it was liaising with healthcare professionals and the HSE on this.
The medicines agency said it was aware of the new Swedish research on a possible stronger link than previously reported between narcolepsy and Pandemrix.
The IMB said these results will be considered in the current review by the European Medicines Agency (EMA), to which it is affiliated, of all available data on the benefit-risk balance of Pandemrix. This review is expected to be completed by the end of the month.
Back in March, the HSE decided to remove all remaining stocks of Pandemrix from GP surgeries in the wake of a reported narcolepsy link.
The latest review by Sweden's drug regulation authority has found that the incidence of narcolepsy is 6.6-fold higher among vaccinated young people than in those unvaccinated. Earlier this year, the same authority reported a four-fold higher risk of getting narcolepsy among children and adolescents who were given Pandemrix.
In its new review, Sweden's Medical Products Agency (MPA) looked at established or suspected cases of the sleeping disorder during 2009-2010, focusing specifically on cases of narcolepsy with cataplexy occurring in children and adolescents under 19.
One hundred and thirty two medical records were reviewed, out of which 81 cases of narcolepsy with cataplexy were included as they had onset of first symptoms within the study period January 2009 and December 2010. Among the included patients, 69, or 85%, had been vaccinated with Pandemrix before onset of the symptoms of the brain disorder.
The Swedish agency said a pattern was noted when examining the occurrence of narcolepsy with cataplexy in the entire population and over the two-year period.
More people developed the first symptoms of narcolepsy during late 2009 and early 2010, in parallel with the swine flu outbreak at the time and national vaccination campaigns in Sweden and other countries, it said.
The latest Swedish figures show that the risk of developing narcolepsy with cataplexy among vaccinated subjects was 4.2 cases per 100,000, compared to only 0.64 cases per 100,000 in unvaccinated people.
The Swedish MPA also said for a few individuals in the study, it was difficult to determine the onset of symptoms in relation to time of vaccination - 'therefore , the magnitude of the increased risk is uncertain and could be higher.'
The IMB said it was in agreement with the view of the EMA that additional data are needed to assess further and to understand the nature of any relationship between the swine flu jab and narcolepsy.
It added that research was ongoing on the possible vaccine-narcolepsy link, including a study across nine EU member states.
The Swedish MPA said the causative mechanisms of the observed increased risk of narcolepsy among vaccinated people could not be explained by its latest study.
"The MPA will therefore collaborate with other authorities and scientists in the planning of further research needed," it added.
It said it would also work to stimulate the introduction of tools for long-term monitoring of the patients who have fallen ill with narcolepsy.