The FDA on Monday added another warning to the label for Johnson & Johnson's single-dose coronavirus vaccine Ad26.COV2.S, this time about an increased risk of Guillain–Barré syndrome (GBS), with health officials describing the side effect as a "small possible risk" for those getting the shot. The move marks another setback for a vaccine that has seen demand fizzle, notably in the US where it had the largest rollout, following production problems and a temporary safety pause over blood clots earlier this year.
According to the US Centers for Disease Control and Prevention (CDC), there have been roughly 100 preliminary reports of GBS detected following some 12.8 million doses of Ad26.COV2.S administered, with cases largely reported about two weeks after vaccination and mostly in men, many aged 50 and older. Almost all of the cases required hospitalisation and one person died, the FDA said. Sources familiar with the FDA's decision said while regulators have found that the likelihood for developing GBS is low, the incidence appears to be about three to five times higher among Ad26.COV2.S recipients than among the general US population.
The suspected cases were reported through the national Vaccine Adverse Event Reporting System (VAERS), which relies on patients and healthcare providers to notify about the adverse effects.
Johnson & Johnson's adenovirus vector vaccine was authorised for emergency use by the FDA in February, becoming the third coronavirus vaccine greenlighted in the US after Pfizer and partner BioNTech's BNT162b2 and Moderna's mRNA-1273, the latter two based on mRNA technology. However, US health officials have found no similar increased risk of GBS with either BNT162b2 and mRNA-1273, after more than 320 million doses of those vaccines have been administered in the US.
The CDC indicated that the Guillain-Barré cases will be discussed as part of an upcoming meeting of advisers to the agency. It noted that even if Johnson & Johnson vaccine does slightly raise the risk of the syndrome, it is still better to get vaccinated against COVID-19. Johnson & Johnson confirmed Monday that it is in discussions with the FDA and other regulators about the GBS cases following immunisation with its vaccine, adding the "chance of having this occur is very low, and the rate of reported cases exceeds the background rate by a small degree."
The FDA also recently attached warnings to the labels of the Pfizer/BioNTech and Moderna coronavirus vaccines after cases of myocarditis and pericarditis occurred in some people who have received those inoculations. Though rare, CDC officials have noted an "imbalance" in these cases of heart inflammation happening in young people in particular.
The new FDA warning is the latest setback for Johnson & Johnson's vaccine. In April, US health officials slapped a pause on its rollout after it was linked to rare cases of thrombosis with thrombocytopenia syndrome. The finding prompted the FDA to add a warning to the vaccine's label in April about the rare blood-clotting disorder. Meanwhile, production has also been stymied after a Baltimore plant run by Johnson & Johnson subcontractor Emergent BioSolutions was shut down earlier this year amid regulatory violations and possible contamination with AstraZeneca's COVID-19 vaccine Vaxzevria, which was also being made there. As a result, Johnson & Johnson has had to toss out millions of Ad26.COV2.S doses.
Alex Gorsky, CEO at Johnson & Johnson, said last month that he was still hopeful that the vaccine would help contain the pandemic overseas. The company has promised up to 400 million doses to the African Union, while the COVAX vaccine-sharing scheme is supposed to receive hundreds of millions of doses. A small laboratory study recently suggested that Ad26.COV2.S protected against the fast-spreading Delta variant of SARS-CoV-2.
Meanwhile, vaccine safety officials in Europe recently recommended that a warning be added about Guillain-Barré to the label for AstraZeneca's vaccine. However, while the safety committee for the European Medicines Agency said that GBS cases have been reported following vaccinations, "at this stage, the available data neither confirms nor rules out a possible association with the vaccine."
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