The news of a link between the Johnson & Johnson vaccine and an exceedingly rare neurological syndrome now under investigation may have some people wondering how many are at risk.
That isn't immediately clear, but the number of people who have reported Guillain-Barré Syndrome, now being investigated as a possible side effect of the single-dose J&J vaccine, is tiny. On top of that, far fewer people in Massachusetts have gotten that vaccine than the two-dose Moderna and Pfizer vaccines.
There have been about 100 reports of Guillain-Barré nationwide, after about 12.8 million people received the vaccine, according to the U.S. Centers for Disease Control and Prevention, which is monitoring the reports along with the Food and Drug Administration.
As of Monday, 281,019 people have received the J&J vaccine in Massachusetts, according to the state's vaccination report, while just under 4 million people have been fully vaccinated with the two doses from Moderna and Pfizer.
Get Boston local news, weather forecasts, lifestyle and entertainment stories to your inbox. Sign up for NBC Boston’s newsletters.
Nationwide, 12.8 million people received the Johnson & Johnson vaccine, while 146.7 million people received the Moderna and Pfizer vaccines -- a similar rate to Massachusetts.
The people who get the syndrome, which causes the body's immune system to attack the nerves, generally recover -- it affects between 3,000 and 6,000 people each year, according to the CDC. Most of the people who reported Guillain-Barré were men, many over 50, and they had the symptoms about two weeks after getting the shot.
Dr. C. Michael Gibson, a Harvard Medical School professor, stressed Monday that that Guillain-Barré Syndrome remains very rare, "not a public health menace."
"The benefits still outweigh the risk of vaccination, particularly with the Pfizer and Moderna vaccines," Gibson said.
Still, Monday's announcement is another mark on the J&J vaccine's record -- it was paused in April while a rare blood clot side effect was investigated.
J&J said in a statement Monday that it has been discussing the reports with the FDA and other health regulators around the world.