The United States’ Centers for Disease Control and Prevention (CDC) and the Food and Drug Administration (FDA) have recommended a “pause” in administration of Johnson & Johnson’s (J&J) single-dose COVID-19 vaccine out of an “abundance of caution” following six cases of a rare type of blood clotting among the 6.8 million US recipients of the vaccine. 

The six reported cases had a rare and severe type of blood clot, called cerebral venous sinus thrombosis (CVST), in addition to low levels of blood platelets (thrombocytopenia). 

The same kind of adverse effect has been noted in Europe among recipients of the AstraZeneca vaccine in Europe – where some 62 cases of the rare disorder have been seen among the 34 million people vaccinated as of 4 April. So far, however, the AstraZeneca vaccine has not been approved in the United States – while the J&J vaccine is only just starting to be rolled out in Europe, following regulatory authorization there in mid-March.   

While an anticoagulant drug called heparin is typically used to treat blood clots, alternative treatments are needed for CVST – which combines clotting with low platelet levels. 

In the case of the J&J jabs, all six cases occurred in women between the ages of 18 and 48, with symptoms occurring 6 – 13 days following vaccination.  That, too, follows a pattern similar to that seen in the AstraZeneca vaccine – where most of the CVST cases were also seen in women under the age of 60 – prompting some countries, like Germany, to halt administration of the vaccine to younger people generally. 

“Right now, these adverse events appear to be extremely rare. COVID-19 vaccine safety is a top priority for the federal government, and we take all reports of health problems following COVID-19 vaccination very seriously,” Dr. Peter Marks, director of the FDA’s Center for Biologics Evaluation and Research, and Dr. Anne Schuchat, principal deputy director of the CDC, said. 

The pause is important to ensure that the health provider community is aware of the potential for these adverse events and can plan for proper recognition and management due to the unique treatment needed for CVST, the agencies’ statement said. 

The European Medicines Agency was the first to announce a review of cases linked to the J&J vaccine on 9 April following four reports of blood clots.  Following a similar review of the AstraZeneca vaccine, the EMA last week reaffirmed that the vaccine was safe for use by all groups – but said that a label should be affixed to the vaccine warning of the rare blood clot potential. 

The White House said in response that the FDA/CDC announcement will not have “significant impact” on US vaccination plans. 

“We are working now with our state and federal partners to get anyone scheduled for a J&J vaccine quickly rescheduled for a Pfizer or Moderna vaccine,” said Jeff Zients, White House COVID-19 Response Coordinator on Johnson & Johnson’s vaccine. 

As of 12 April, more than 6.8 million doses of the Johnson and Johnson vaccine have been administered in the US, making up less than 5% of recorded doses in the country. The US currently has secured Pfizer and Moderna vaccines for 300 million Americans. 

The CDC will convene in a meeting on Wednesday to further review the cases. The FDA will then review the analysis while also investigating cases. 

In a company statement,  Johnson & Johnson said that it is  “aware“ of the adverse events that occur from administration of the vaccine, and is working with medical experts and health authorities in both Europe and the US through the investigation. 

“We have been working closely with medical experts and health authorities, and we strongly support the open communication of this information to healthcare professionals and the public,” the company said in its statement.

Image Credits: Johnson & Johnson, NBC News.