Posted on behalf of Chloe McIvor.
The adjuvanted vaccines used during the 2009 swine flu (H1N1) pandemic did not significantly increase the risk of Guillain-Barré syndrome, a large, multinational study, commissioned by the European Centre for Disease Prevention and Control (ECDC), concludes today in the British Medical Journal.
The vaccine-related concerns stem from the sevenfold increase in Guillain-Barré syndrome experienced during the US pandemic H1N1 flu vaccine campaign of 1976. Guillain-Barré syndrome is a rare neurological disorder, which can result in severe nerve damage caused by the body’s own immune system. Adjuvanted vaccines contain substances that stimulate the immune system to boost the efficacy of the vaccine. After the 1976 vaccine was abruptly discontinued, flu vaccines became controversially linked to Guillain-Barré syndrome, even though no or little risk was found in studies on subsequent seasonal flu vaccines.
The consortium conducted the study across five European countries which launched vaccination campaigns against the 2009 pandemic; a total sample of 50 million people. They reassuringly found that any risk of Guillain-Barré syndrome is negligible. The risk is estimated to be less than three excess cases of Guillain-Barré syndrome for every million people protected by the vaccine.
Although most current seasonal flu vaccines do not contain an adjuvant, this sort of large-scale safety analysis is important for assessing the potential use of adjuvanated vaccines in the future.