The case for a link between a vaccine used during the 2009 H1NI ‘swine flu’ pandemic and a serious sleeping disorder known as narcolepsy was bolstered by a study published yesterday.
Studies in several other countries have found an association between administration of GlaxoSmithKline’s Pandemrix and narcolepsy, a disorder causing excessive daytime sleepiness, which in turn is often accompanied by cataplexy — sudden muscle weakness. Now, in a small study published in the British Medical Journal, researchers have found further evidence of the link in some patients with narcolepsy in the United Kingdom.
The team reviewed case notes for 245 people, aged from 4 to 18 years old, from sleep and neurology centres in England. Seventy-five of the people had developed narcolepsy since the beginning of 2008 and 11 had been vaccinated with Pandemrix. From this, the researchers concluded that the vaccine caused a 14-to-16-fold increase in risk of narcolepsy, which they estimate would correspond to 1 in 52,000–57,500 vaccinations being associated with narcolepsy.
The association between Pandemrix and narcolepsy has become well established since the first reports in Sweden and Finland in 2011. Two Europe-wide reviews providing further analysis of the link between Pandemrix and narcolepsy (summary) were published last September by the Vaccine Adverse Events Surveillance and Communication consortium, funded by the European Centre for Disease Control and Prevention (see here and here for the full reports).
The association found will require further investigation into the safety of the ASO3 adjuvant formula used in Pandemrix. Such additives are used in some vaccines to boost the immune response so that each vaccine dose can be smaller, allowing global vaccine capacity to be stretched to cover several times as many people. Without that multiplier effect, there would in a pandemic be only enough vaccine to cover a fraction of the world’s population (for some of Nature‘s stories on this issue during the 2009 H1N1 pandemic, see ‘Regulators face tough flu-jab choices‘, ‘US ramps up swine flu protection‘, ‘US puts flu vaccines on trial‘ and ‘Vaccine decisions loom for new flu strain‘).
But ultimately the situation remains the same as Nature reported in 2011:
Side effects of vaccines are part of any public health response risk equation. No amount of clinical trials can detect rare side-effects in advance, as statistically one would need impractically large population-size experimental cohorts to pick up very low incidence rates. Instead, regulators use pharmacovigilance once vaccines have been deployed to spot early on any problems. With some 30.8 million Europeans, including this author, already vaccinated with Pandemrix since autumn 2009, no serious safety concern has been detected.
Although anti-vaccine groups will no doubt leap on the preliminary reports from Scandinavia to scream “side-effects,” the sober reality is that not using modern and safe vaccines causes many more people to become ill or die than any rare side-effect.