A ProMED-mail post
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International Society for Infectious Diseases
Date: Tue 8 Feb 2011
Source: World Health Organization (WHO), Global Advisory Committee on
Vaccine Safety [edited]
Since August 2010, following widespread use of vaccines against influenza
A/(H1N1) 2009, cases of narcolepsy, especially in children and adolescents,
have been reported from at least 12 countries.
Narcolepsy is a rare sleep disorder that causes a person to fall asleep
suddenly and unexpectedly. The rates reported from Sweden, Finland, and
Iceland have been notably higher than those from other countries.
The National Institute for Health and Welfare of Finland issued a
preliminary statement on 1 Feb 2011 following an investigation into the
cases in Finland. A systematic retrospective registry-based review was
conducted of all new narcolepsy cases diagnosed during 2006-2010, and cases
in 2009-2010, born in 1990 or later, were reviewed using newly developed
Brighton collaboration criteria for the disease. During 2009-2010 they
found a higher risk of narcolepsy among those aged 4-19 years old who had
received the vaccination against influenza A/(H1N1) 2009 compared with
those who had not been vaccinated. The only pandemic vaccine used in
Finland was Pandemrix, an adjuvanted influenza (H1N1) 2009 monovalent
vaccine manufactured by GlaxoSmithKline.
Pandemrix vaccine was used in 47 countries worldwide during the 2009-2010
season. Studies are ongoing to determine whether the apparent increased
risk of narcolepsy reported in Sweden is higher in vaccinated persons.
The National Institute in Finland (on the advice of the Finnish National
Narcolepsy Task Force) has concluded that the risk of developing narcolepsy
among those vaccinated aged between 4 and 19 years is about 9 times greater
than those unvaccinated in the same age group, corresponding to a risk of
about one case of narcolepsy per 12 000 vaccinated in this age group. The
increased risk has not been seen in younger or older age groups.
Narcolepsy is a condition that has a strong genetic linkage, being almost
uniquely seen in persons who have the (HLA) DQB1*0602 genotype [probably
about 25 per cent of most populations - Mod.CP]. Of the cases of narcolepsy
tested so far in Finland (n=22) diagnosed during 2009-2010, all have that
genotype.
The National Institute considers it probable that the Pandemrix vaccine was
a contributing factor to this observed increase and has called for further
investigation of other co-factors that may be associated with the increased
risk. They consider it most likely that the Pandemrix vaccine increased the
risk of narcolepsy in a joint effect in those genetically disposed with
some other, still unknown, genetic and/or environmental factor. The final
report from the Finnish National Narcolepsy Task Force is expected by 31
Aug 2011.
WHO's Global Advisory Committee on Vaccine Safety (GACVS) reviewed this
data by telephone conference on 4 Feb 2011. GACVS agrees that further
investigation is warranted concerning narcolepsy and vaccination against
influenza (H1N1) 2009 with Pandemrix and other pandemic H1N1 vaccines.
An increased risk of narcolepsy has not been observed in association with
the use of any vaccines, whether against influenza or other diseases, in
the past. Even at this stage, it does not appear that narcolepsy following
vaccination against pandemic influenza is a general worldwide phenomenon,
and this complicates interpretation of the findings in Finland.
In collaboration with a number of European Union member states, the
European Centre for Disease Prevention and Control (ECDC) is currently
conducting epidemiological studies of narcolepsy and pandemic influenza
vaccines. The findings from these studies and others, including further
investigations in Finland, may help clarify the determinants of any
increased risk of narcolepsy, which currently appears to be restricted to
the months following vaccination and by age group and country.
GACVS will continue to monitor the situation closely, and updates will be
provided as further information becomes available and is assessed.
--
communicated by:
ProMED-mail
[Further information can be found in the Statement from the National
Institute for Health and Welfare of Finland from 1 Feb 2011 at:
Details of the Brighton Collaboration Criteria can be found at: The
Brighton Collaboration: Creating a Global Standard for Case Definitions
(and Guidelines) for Adverse Events Following Immunization
(
A description of narcolepsy can be found in PubMed Health at:
[see also:
Influenza (11): Europe, UK, WHO 20110206.0421
2010
---
Influenza pandemic (H1N1) (66): Sweden, no vaccine narcolepsy link
20100914.3322
Influenza pandemic (H1N1) (65): Sweden, Finland, vaccine react. 20100904.3178]
.................. cp/msp/sh
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