The researchers found that children who had been immunized were 14.4 times as likely to develop narcolepsy as were similar children who had not been immunized. The figure of 14.4 is very similar to that found in Finland, where it was 13 times. The association might not be causative, of course: for example, if the immunization merely brought forward the development of the narcolepsy in children that would have developed in any case at a later stage in the children’s lives. Nor can we yet say whether narcolepsy developing within a few months of immunization with this influenza vaccine will last the rest of the child’s life, remit, or get worse.
The relative shortness of the follow-up did not allow for the possibility to be excluded that the immunization only brought forward the development of narcolepsy, but the authors nonetheless felt — for what such a feeling is worth — that the relationship was indeed a causative one.
The increased risk of narcolepsy, even if the association were a causative one, does not settle the issue of whether the vaccine should continue to be used. Even though the relative risk was very high, the absolute risk — estimated at about one per 55,000 doses — is small. And since the vaccine has proved very effective against the type of flu it is supposed to protect against, which can itself kill or severely harm the vulnerable, it might still save life or disability. In medicine, as in life in general, there is no gain without pain.
There is little doubt, however, that the findings will be grist to a mill that has now been grinding for more than 200 years, and that (remarkable to record) gave rise to mass protest movements in the nineteenth century in Britain and America.
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