Solving Johnson & Johnson’s clot mystery

On April 13, two American public health agencies pulled the plug on the Johnson & Johnson COVID-19 vaccine citing concerns about blood clots in younger women. Just over a week later, the Centers for Disease Control and Prevention and the Food and Drug Administration both gave the go ahead for Johnson & Johnson vaccines to continue.

Now a group of German scientists think they may have figured out why the American-made vaccine as well as Britain’s AstraZeneca vaccine cause blood clots in rare cases. Researchers from Germany’s Goethe University published a report on May 26 blaming the vaccines’ delivery system. But the discovery may come too late to rebuild the eroded confidence in Johnson & Johnson’s shot.

Both Johnson & Johnson and AstraZeneca use a weakened common cold virus—called an adenovirus—to transport a COVID-19 spike protein into the human body in their vaccines. While Pfizer and Moderna’s two-shot mRNA vaccines deliver genetic material to the fluid inside a cell, the adenovirus formulas deliver the spike protein inside a cell’s nucleus.

In May, the CDC reported 28 cases of serious blood clots out of 8.7 million doses of the Johnson & Johnson vaccine administered, with most of the cases among women aged 18 to 49. Similarly rare clotting problems have been reported in Europe, where the AstraZeneca vaccine is widely used.

According to the German researchers, the spike proteins in the adenovirus vaccines can break apart inside a cell’s nucleus, enter the blood stream and in very rare cases cause clots. Lead author Rolf Marschalek said companies making this kind of vaccine could alter the design to reduce risk.

But it may be too late to fix the damage to the Johnson & Johnson vaccine’s reputation. The Kaiser Family Foundation conducted a poll in April and found only 15 percent of Americans were very confident in the safety of the Johnson & Johnson vaccine. By comparison, the same survey found 37 percent and 38 percent of respondents very confident in the safety of the Moderna and Pfizer vaccine, respectively.

Scattered anecdotal evidence from across the country suggests the reports of blood clots among Johnson & Johnson vaccine recipients have withered demand for the product. State health officials in Arkansas recently said 60,000 of the shots in the state’s possession could expire soon unless health officials find takers. Officials in Bucks County, Pa., resorted to handing out shaved ice coupons in May to try and get expiring Johnson & Johnson vaccines into arms. According to WPVI-TV, several suburban Philadelphia counties were sitting on thousands of expiring vaccines at the end of May. “I think there were a lot of people on the fence and that pause made some of those people move off the fence, and we’ve got to get them back on,” Bucks County Health Director David Damsker told WPVI-TV.