[5] Pandemrix was found to be associated with an increased risk of narcolepsy[6] following investigations by Swedish and Finnish health authorities[7] and had higher rates of adverse events than other vaccines for H1N1.
[9] Stanford University studies suggested that narcolepsy is an autoimmune disease[10] and that it appears to be triggered by upper airway respiratory infections.
[13] While other 2009 H1N1 vaccines have been developed, the use of a proprietary immunologic adjuvant is claimed to boost the potency of the body's immune response, meaning that only a quarter of the inactivated virus is needed.
[16] Subsequent testing has allowed the UK programme to consist of just a single dose for most people, with a two-dose schedule for children under the age of 10 years and immunocompromised adults.
[18][19] The Marketing Authorisation from the European Medicines Agency expired in August 2015 when GSK Biologicals did not apply for renewal of it citing lack of demand for the vaccine.
[6] In 2018, it was demonstrated that T-cells stimulated by Pandemrix were cross-reactive by molecular mimicry with part of the hypocretin peptide, the loss of which is associated with type I narcolepsy.
[27] In August 2010, The Swedish Medical Products Agency (MPA) and The Finnish National Institute for Health and Welfare (THL) launched investigations regarding the development of narcolepsy as a possible side effect to Pandemrix flu vaccination in children.
[7] In summer 2010, the MPA and THL received reports from Swedish and Finnish healthcare professionals that narcolepsy was a suspected adverse drug reaction to the Pandemrix flu vaccination.
[31] In August 2010 the Swedish MPA issued a statement which included the following: "An investigation is ongoing, but any relationship between the vaccination and the reported symptoms can not be concluded.
[citation needed] A study by the Stanford University School of Medicine examined the incidence of narcolepsy in relation to upper airway infection and a H1N1 vaccine (not Pandemrix) in Chinese patients.
[37] However, the original scientific article claiming that HA protein in both the virus and the vaccine could, in some people, trigger an immune reaction against hypocretin, was retracted in 2014 because the data could not be reproduced.
[39][40] In 2014, a Finnish group published results that showed Pandemrix contained a higher amounts of structurally altered viral nucleoproteins than Arepanrix, a similar vaccine not associated with narcolepsy.
[42] In 2018, a multinational study including Centers for Disease Control and Prevention scientists published safety data on adjuvanted pH1N1 vaccines.
[43] In December 2018, T-cells were demonstrated to be cross-reactive to both a particular piece of the pandemic 2009 H1N1 virus and the amidated terminal ends of hypocretin peptides, the loss of which is associated with type I narcolepsy.