The US Food and Drug Administration updated its warning labels for the Johnson & Johnson COVID-19 vaccine to include information of the possible "increased risk" of a rare neurological disorder known as Guillain-Barré syndrome.
The FDA said it's not entirely clear the vaccine caused the syndrome, but noted an increase in reports of the sometimes paralyzing condition.
The FDA said in a statement on Monday that the warning was added after 100 reports of the rare condition among people who had received the shot. So far, about 12.8 million people in the US have been given Janssen vaccines.
It said that 95 of the 100 cases required hospitalisation and that one person had died.
What does the revised FDA label say?
"Reports of adverse events following use of the Janssen COVID-19 Vaccine under emergency use authorization suggest an increased risk of Guillain-Barré syndrome during the 42 days following vaccination," the updated label says.
"Although the available evidence suggests an association between the Janssen vaccine and increased risk of GBS, it is insufficient to establish a causal relationship. No similar signal has been identified with the Moderna and Pfizer-BioNTech COVID-19 vaccines," it adds.
What is Guillain-Barré Syndrome (GBS)?
According to the Centers for Disease Control and Prevention (CDC), Guillain-Barré Syndrome is a rare, autoimmune disorder in which a person’s own immune system damages the nerves, causing muscle weakness and sometimes paralysis.
The condition can cause symptoms that last for a few weeks to several years. While most people recover completely, some have permanent nerve damage and some people have died, too, it says.
What are the symptoms?
People with this syndrome usually first experience weakness or tingling sensations in both legs. In many cases, this spreads to the arms and upper body, the CDC says.
As it progresses, it can reach a point where some muscles cannot be used at all, and, in severe cases, the person can become paralysed.
Symptoms can progress over hours, days, or weeks, and weakness typically peaks within the first two weeks after symptoms appear. Recovery may take as little as a few weeks or as long as a few years, the CDC says.
J&J says while the chance of having this is very low, you should seek medical attention right away if you develop any of the following symptoms:
Weakness or tingling sensations, especially in the legs or arms, that’s worsening and spreading to other parts of the body
Difficulty walking
Difficulty with facial movements, including speaking, chewing, or swallowing
Double vision or inability to move eyes
Difficulty with bladder control or bowel function
What causes Guillain-Barré Syndrome?
According to the World Health Organisation (WHO), GBS is often observed after an infection - viral or bacterial.
It may also be triggered by vaccine administration or surgery, it says.
About two-thirds of people with GBS had diarrhea or a respiratory illness several weeks before developing symptoms, the CDC says.
Infection with Campylobacter jejuni, which causes diarrhea, is one of the most common risk factors.
Flu, cytomegalovirus, Epstein Barr virus, and Zika virus can also cause it.
Who is more at risk?
People of all ages can be affected, but it is more common in adults and in males.
How common is GBS?
The condition is rare, affecting only about 1 in 100,000 people.
An estimated 3,000-6,000 people develop GBS each year in the US, the CDC says.
What is the treatment?
Since the condition is life-threatening, the patients should be hospitalised in order to be monitored closely, the WHO says.
There is no known cure for GBS. However, treatments can help improve symptoms and shorten its duration.
Common treatments include plasma exchange and high-dose immunoglobulin therapy.
Supportive care includes monitoring of breathing, heartbeat and blood pressure.
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