It will be interesting to see if in the years to come, there is a reduction in the rate of new narcolepsy in this exposed population. In other words, did this exposure simply accelerate the development of narcolepsy into the period immediately following the exposure, or are these new cases that would not have happened without the exposure.

It may be that, as you suggest, the pool of genetically-susceptible people can be depleted by exposure, and that, following an extensive, population-wide exposure, the incidence of narcolepsy will decrease for some subsequent years.

http://onlinelibrary.wiley.com/doi/10.1002/ana.23799/abstract;jsessionid=36FA2AD0EACFD9C59D72E4D5AD23D808.d03t03

BTW, Mignot et al. have shown that narcolepsy tracks (months later) with seasonal respiratory diseases such as influenza in China, where the incidence of narcolepsy tripled during the H1N1 pandemic:

http://www.ncbi.nlm.nih.gov/pubmed/21866560

The vaccination rate was about 60% in Sweden.* The possible problem with Pandemrix has been debated very much and still is. I am sorry to say that most of the public debate now focus on whether the government should be held responsible for the alleged raise in narcolepsy and thus “pay up”. I am not quite sure for what though, since we have (more or less) free health care, extra family expenses perhaps.

I do not know if “genetics” could play a role at all in this case. But if so, it would be interesting to see some statistics about it. Sweden has been, and still is, mostly populated with people who is related to each other. Moreover, we did spread into Finland not that long ago. A rough guess would be that about 10% Finns is of Swedish heritage. **

@Janet
They have. More importantly, one of Sweden’s most wide spread daily “serious” news papers has been campaigning against the national vaccination policy (and at the same time scaring people due to blunt reporting). I have not yet seen any numbers if the campaign has had any effect on the different vaccination rates though.

* The source has ISBN: 978-91-86585-91-4 (its in Swedish though =)
** I am way out of my comfort zone “knowledge-wise” here

My sense is, though – probably not. The pool of people with the HLA predisposition is much greater than the number of people who develop narcolepsy. So I don’t think this episode depleted the pool of susceptibles appreciably, but it would be interesting to see specific numbers on this.

This virus was expected to be extremely problematic, which was why the new virus was rushed into vaccine production.

There are autoimmune neurological disorders that can be triggered by infections, for example PANDAS. Presumably it is not the infection per se, but rather the immune system response that triggers the autoimmunity.

It may be that trace levels of specific bacterial antigens in different lots of vaccine were sufficient to trigger narcolepsy in susceptible individuals due to the conflation of multiple circumstances, including the immunological naivety of those affected. However there was also an association with infection by the virus which would imply a viral antigen, or virus infection acting as an adjuvant to cause sensitization to antigens from resident bacteria.

It will be interesting to see if in the years to come, there is a reduction in the rate of new narcolepsy in this exposed population. In other words, did this exposure simply accelerate the development of narcolepsy into the period immediately following the exposure, or are these new cases that would not have happened without the exposure. But that will take pretty good followup because the rates are so low.

“During 2009-2010 [Finnish authorities] found that the risk of narcolepsy among people aged 4-19 years old who had received pandemic influenza vaccine was nine times higher than that among those who had not been vaccinated. This corresponds to a risk of about 1 case of narcolepsy per 12,000 vaccinated in this age group. No increased risk has been seen in younger or older age groups.”

In the same report Swedish authorities cited a 3 per 100,000 rate among vaccinated individuals.

I was not easily able to find the vaccination rates for these countries, much less the rates for these particular demographics. Seems like a very small signal in a very noisy data set.

The observation that the (HLA) DQB1*0602 genotype is nearly universal among those developing narcolepsy is interesting in a gross sense but without more information about the distribution of that genotype in the larger population it seems more a curiosity than a clue.

I hope some of the commenters will have some additional light to shed.

*http://www.who.int/vaccine_safety/committee/topics/influenza/pandemic/h1n1_safety_assessing/narcolepsy_statement/en/index.html

Thanks for the details; this is bound to pop up in anti-vax circles.