There is no evidence to link GlaxoSmithKline's H1N1 swine flu vaccine Pandemrix to cases of narcolepsy, European drugs regulators said on Thursday, but a full review is needed and will take three to six months.
The European Medicines Agency (EMA) said its Committee for Medicinal Products for Human Use had reviewed all available data on the suspected link between narcolepsy and Pandemrix.
"The committee concluded that the available evidence was insufficient to determine whether there is any link between Pandemrix and reports of narcolepsy, and that further studies were necessary to fully understand this issue," it said in a statement.
Narcolepsy is a rare sleep disorder that causes a person to fall asleep suddenly and unexpectedly. Its precise cause is unknown, but it is generally considered to be triggered by a combination of genetic and environmental factors.
Glaxo said in a statement that the total number of cases of narcolepsy following immunization with Pandemrix reported to it as of September 17, 2010, was 80, the majority of which were from Sweden and Finland.
Pandemrix has been used since September 2009 for vaccination against H1N1 pandemic flu, also known as swine flu, and has been given to at least 30.8 million Europeans.
"We will also continue our own investigation in an effort to gather additional data and information regarding the reported cases," Norman Begg, chief medical officer at GSK Biologicals, said in a statement.