In the United States alone, 300,000 to 600,000 people develop blood clots each year, according to C.D.C. Data. However, the particular bleeding disorder known as cerebral venous sinus thrombosis developed by vaccine recipients is extremely rare.
All women developed the disease within about two weeks of being vaccinated, and government experts are concerned that an immune system response triggered by the vaccine was the cause. Federal officials said there was broad agreement in the higher echelons of administration about the need to suspend vaccine use while cases are being investigated.
The decision is a new blow for Johnson & Johnson. Late last month, the company discovered that employees at a subcontracted facility in Baltimore had accidentally contaminated a batch of vaccine, forcing the company to throw away the equivalent of 13-15 million cans. That facility would handle the delivery of the vaccine to the US from Johnson & Johnson’s Dutch plants, which were federal certified earlier this year.
The certification of the Baltimore plant by the F.D.A. has now been delayed while inspectors investigate quality control issues, greatly reducing the supply of Johnson & Johnson vaccines. The sudden drop in available doses sparked widespread complaints from governors and state health officials who had expected much larger deliveries of Johnson & Johnson’s vaccine this week than they did.
States have used the vaccine in a variety of settings, including at mass vaccination sites and on college campuses. The vaccine’s one-shot approach has proven popular, and officials have directed it to temporary, rural, and isolated communities where tracking a second dose is more complicated.
It is common for regulators to investigate “safety signals” in new vaccines and other medical products. The signals very often turn out to be of no concern. However, concerns about Johnson & Johnson’s vaccine echoes concerns about AstraZeneca, which European regulators investigated last month after some recipients developed blood clots.
Of 34 million people who received the vaccine in the UK, the European Union and three other countries, 222 had blood clots associated with low platelet levels. The majority of these cases occurred within the first 14 days after vaccination, mainly in women under 60 years of age.