A new study finds that the H1N1 (swine flu) vaccine in the U.S., which was given out in 2009, was associated with a small increased risk of developing the rare paralyzing disease Guillain-Barré syndrome. However, the authors note that the benefits of the vaccine outweigh the risks.
Guillain Barré syndrome is a disorder which affects the peripheral nervous system, it is characterized as symmetrical weakness, usually affecting the lower limbs first and then progressing to other parts of the body.
The syndrome occurs when the body attacks nerves which are essential for movement and respiration. Although the condition is serious and can take months to recover from, almost 80% of patients end up making a full recovery.
The study, which was published in The Lancet, aimed to identify whether there was any link between the mass 2009 H1N1 vaccination programe in the USA and increased risk of developing Guillain Barré syndrome.
They gathered data from six different adverse event monitoring systems to evaluate the safety of the H1N1 vaccine. The researchers, led by Dr Daniel Salmon, of the National Vaccine Program Office, US Department of Health and Human Services, looked at the prevalence of Guillain-Bare syndrome among the 23 million people who were vaccinated.
A total of 77 people developed Guillain Barré syndrome after 91 days of receiving the vaccination. The incidence of the syndrome was 2.35 times higher within the first 42 days of vaccination compared to after that period. Guillain Barré syndrome usually affects one in every hundred thousand people, which means the vaccination accounted for an excess 1.6 people per million developing the condition.
Dr Salmon said:
“On an individual level, we cannot predict with certainty who will contract influenza, who will have a serious complication or die from the disease, or who will have a very rare but serious adverse event from the vaccine. The safety monitoring programme for influenza A (H1N1) 2009 monovalent inactivated vaccine did not identify any other serious adverse events associated with the vaccine.”
The 2009, the H1N1 “Swine flu” pandemic infected close to 61 million people in the USA. H1N1 infection caused 274,000 admissions and 12,470 deaths.
A previous study indicated that the vaccination program prevented close to a million cases of H1N1, saving up to 500 lives. According to an article in PLoS Medicine, the vaccine was extremely effective at protecting people against the pandemic.
Dr Salmon concluded:
“Clinicians, policy makers, and those eligible for vaccination must consider the overall risks and benefits of vaccination, as defined by epidemiological studies, but should be assured that the benefits of influenza A (H1N1) 2009 monovalent inactivated vaccines greatly outweighed the risks.”
Interestingly another study in the British Medical Journal, reported that the H1N1 vaccine did not lead to the development of Guillain-Barre syndrome.
Written by Joseph Nordqvist