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Guillain-Barré Syndrome (GBS) is a rare, occasionally deadly, neurological disorder that gained notoriety in 1976 after it was linked to an emergency flu vaccine that was rolled out in anticipation of a `swine flu’ pandemic.
As it turned out, the feared pandemic never came.
But before the campaign was abandoned - among the 40 million people who were vaccinated - around 500 people developed GBS and 25 died.
While not all of those cases were likely caused by the vaccine, the incidence of Guillain-Barré Syndrome was around 1 in every 100,000 vaccinations. Or five times the expected background rate of this disease.
I was a young paramedic at the time, and chronicled my small part in that bit of influenza history some time ago in Deja Flu, All Over Again.
In the United States, somewhere between 3,000 and 6,000 people develop the disorder each year. While most GBS victims fully recover, some people are left with permanent nerve damage.
This from the CDC Guillain-Barré page.
What causes GBS?
Many things can cause GBS; about two-thirds of people who develop GBS symptoms do so several days or weeks after they have been sick with diarrhea or a respiratory illness. Infection with the bacterium Campylobacter jejuni is one of the most common risk factors for GBS. People also can develop GBS after having the flu or other infections (such as cytomegalovirus and Epstein Barr virus). On very rare occasions, they may develop GBS in the days or weeks after getting a vaccination.
In 2010 studies showed you are many times more likely to develop GBS in the weeks following an influenza infection, than you are after getting the flu vaccine (see Lancet: The Influenza - Guillain Barré Syndrome Connection).
Still, some risk of developing GBS is assumed likely with flu vaccines, although most years it is too small to measure.
Today, The Lancet has published a meta-analysis on the 2009 unadjuvanted monovalent pandemic flu vaccine and its association with GBS, finding a `small increase’ in risk.
Association between Guillain-Barré syndrome and influenza A (H1N1) 2009 monovalent inactivated vaccines in the USA: a meta-analysis
Dr Daniel A Salmon PhD. Michael Proschan PhD , Richard Forshee PhD , Paul Gargiullo PhD , William Bleser MSPH , Dale R Burwen MD , Francesca Cunningham PharmD , Patrick Garman PhD , Sharon K Greene PhD , Grace M Lee MD , Claudia Vellozzi MD f, W Katherine Yih PhD , Bruce Gellin MD , Nicole Lurie MD , the H1N1 GBS Meta-Analysis Working Group†
Summary
Background
The influenza A (H1N1) 2009 monovalent vaccination programme was the largest mass vaccination initiative in recent US history. Commensurate with the size and scope of the vaccination programme, a project to monitor vaccine adverse events was undertaken, the most comprehensive safety surveillance agenda in the USA to date. The adverse event monitoring project identified an increased risk of Guillain-Barré syndrome after vaccination; however, some individual variability in results was noted. Guillain-Barré syndrome is a rare but serious health disorder in which a person's own immune system damages their nerve cells, causing muscle weakness, sometimes paralysis, and infrequently death. We did a meta-analysis of data from the adverse event monitoring project to ascertain whether influenza A (H1N1) 2009 monovalent inactivated vaccines used in the USA increased the risk of Guillain-Barré syndrome.
Methods
Data were obtained from six adverse event monitoring systems. About 23 million vaccinated people were included in the analysis. The primary analysis entailed calculation of incidence rate ratios and attributable risks of excess cases of Guillain-Barré syndrome per million vaccinations. We used a self-controlled risk-interval design.
Findings
Influenza A (H1N1) 2009 monovalent inactivated vaccines were associated with a small increased risk of Guillain-Barré syndrome (incidence rate ratio 2·35, 95% CI 1·42—4·01, p=0·0003). This finding translated to about 1·6 excess cases of Guillain-Barré syndrome per million people vaccinated.
Interpretation
The modest risk of Guillain-Barré syndrome attributed to vaccination is consistent with previous estimates of the disorder after seasonal influenza vaccination. A risk of this small magnitude would be difficult to capture during routine seasonal influenza vaccine programmes, which have extensive, but comparatively less, safety monitoring. In view of the morbidity and mortality caused by 2009 H1N1 influenza and the effectiveness of the vaccine, clinicians, policy makers, and those eligible for vaccination should be assured that the benefits of inactivated pandemic vaccines greatly outweigh the risks.
Funding
US Federal Government.
Based on these numbers, the U.S. might have seen an additional 100-150 cases of GBS due to the rollout of the monovalent pandemic flu shot. Of those, 80% would be expected to recover completely.
There is no such thing as a 100% benign, completely safe drug.
Yesterday, in FDA: Drug Safety Communication On Azithromycin & Cardiac Risk, we looked at the small risk of adverse cardiac arrhythmias associated with a very popular – and lifesaving – antibiotic.
Every year, thousands of people die, or experience serious complications, as a result of taking over-the-counter (OTC) medications.
Prescription drugs, being generally stronger, are even more problematic. It is always a balancing act - a risk-reward calculation - when deciding to take any drug.
Regarding the risks of taking the 2009 H1N1 monovalent shot - balanced against a possible increase of 1.6 cases of GBS per million vaccine recipients - we must compare:
The CDC has estimated that the 2009 pandemic flu infected more than 60 million Americans. The virus hospitalized more than 200,000, and killed more than 12,000 (most under the age of 65).
Harder to measure, but Influenza infections have been linked to increases in Narcolepsy (cite Narcolepsy Onset is Seasonal and Increased Following the H1N1 Pandemic in China).
Influenza infections have also been linked to GBS and developing Parkinson’s Syndrome later in life (Revisiting The Influenza-Parkinson’s Link).
While there were other, mostly minor and temporary adverse effects linked to the flu shot - even if we assume a modest 50% effectiveness at preventing infection – when it comes to seeing a good outcome, the flu shot wins by a mile.
That is not to say that the flu shot is perfect. Most years it provides `moderate’ protection, and this year we are seeing particularly disappointing Vaccine Effectiveness (VE) numbers (see Helen Branswell CP article Flu shot gave minimal help to seniors).
As we’ve discussed often, there is a pressing need for better flu vaccines (see CIDRAP: The Need For `Game Changing’ Flu Vaccines).
But until they can be developed - the flu shots available now have an enviable safety record - and the CDC considers it to be the best single preventative action you can take against the flu.
