The 2009 swine flu pandemic (and panic) has been forgotten by most, but regulators, global health organisations and pharmaceutical companies are continuing post-pandemic activities, which include keeping an eye on new cases of the illness and monitoring the safety of pandemic vaccines.
This week, swine flu returned to headlines after two studies published in the Public Library of Science appeared to confirm a link between GlaxoSmithKline’s Pandemrix vaccine and cases of narcolepsy in children in Finland. Between 2002 and 2009, instances of narcolepsy were around 0.31 per 100,000 people. In 2010, this jumped to 5.3 cases per 100,000, which equates to a 17-fold increase.
Regulators have been aware of the link for some time. In July 2011, the European Medicines Agency (EMA) finalised a safety review of Pandemrix, Although the overall risk–benefit balance of the vaccine remains positive, the EMA recommended that it should not be used in persons under 20 years of age unless a seasonal trivalent influenza vaccine is not available, or if an H1N1 vaccination is required.
But the problem is that the link is not well understood. Pandemrix was used in dozens of countries, but the spike in narcolepsy cases only seems to be prevalent in Finland and Sweden. In Canada, an equivalent H1N1 vaccine (Arepanrix; also manufactured by GSK) was widely used, but did not seem to trigger an increase in narcolepsy cases. It is believed that Pandemrix interacted with genetic or environmental factors, which raised the risk of narcolepsy.
According to media reports, the governments of other countries are aware of the study results and other research is taking place.
The situation is a prime example of the importance of genetic factors on pharmaceutical products. A growing trend in the industry is for companies to explore the possibilities of personalised medicine, which involves matching the right patient with the right treatment. This is already being done for some medicines, including cancer medicines, using diagnostic tests.
Unfortunately, Pandemrix has a long way to go before such a test can be developed, since it is still not known exactly how the vaccine is linked to narcolepsy. To complicate matters narcolepsy itself is also not very well understood. However, GSK is reported to be conducting more studies in order to further explore the link between its vaccine and narcolepsy.