The US Centers for Disease Control and Prevention (CDC) and Food and Drug Administration (FDA) have recommended a pause of inoculation with Johnson & Johnson’s (J&J) Covid-19 vaccine over blood clots.

So far, over 6.8 million doses of the vaccine have been administered in the country and the federal agencies are reviewing data on the reported rare blood clot cases.

The latest development comes after six women under the age of 50 years developed the clots on receiving the vaccine.

In these individuals, a type of blood clot called cerebral venous sinus thrombosis (CVST) was seen along with reduced blood platelet levels called thrombocytopenia.

All six cases were among women aged between 18 and 48 years with the onset of symptoms occurring six to 13 days on receiving the shot.

Furthermore, J&J has decided to delay the vaccine rollout in Europe and halt vaccinations in all clinical trials until the company provides updated guidance for investigators and participants.

The European Medicines Agency (EMA) already initiated a review of the single-shot Covid-19 vaccine.

South Africa has also put the use of this vaccine on hold.

Reuters quoted acting US FDA commissioner Janet Woodcock as saying that the pause is expected to be for a matter of days and was aimed at keeping healthcare providers informed on how to diagnose and treat the clots.

Earlier, European regulators had identified a potential link between AstraZeneca’s Covid-19 vaccine and a similar rare blood clotting issue that caused death in some people receiving the vaccine.

FDA official Peter Marks said it was ‘plainly obvious’ the J&J blood clot cases were ‘very similar’ to the ones potentially caused by the AstraZeneca vaccine.

No such blood clot issues were seen among people who were given the Moderna or Pfizer/BioNTech Covid-19 vaccines that utilise a different technology and accounted for most vaccinations in the country so far, he added.

As two Covid-19 vaccines are being reviewed for the potential association to rare blood clots, the US Government researchers will analyse if the specific technology behind the jabs is causing the risk.