Federal regulators have severely restricted who can get the Johnson & Johnson COVID-19 vaccine. The U.S. Food and Drug Administration cites ongoing concerns over rare, but serious blood clots.
The FDA said adults should only get the J&J vaccine if they specifically request it or can't get an alternate vaccine.
"Post drug release surveillance is very, very important, they had picked up on this," said Dr. Brian Roberts with Urgent Care in San Luis Obispo.
New data is leading to more restrictions on the one-shot Johnson & Johnson vaccine.
At issue is Thrombosis, a rare but potentially deadly blood clot.
For the general population, there are about three cases per million doses of vaccine.
That number increases to eight cases per million doses for women between the ages of 30 and 50.
The death rate for that group is about one in a million.
So far, there have been 60 known cases with nine fatalities.
"What the FDA has done is they've looked at the other vaccines, specifically those from Pfizer/ Moderna and it has shown that the risk profile for J&J while very good, isn't quite as good as the risk profile for Pfizer and Moderna," said Scott Robertson, President, and CEO of Pacific Central Coast Health Centers in Santa Maria.
Health officials noted that they do not know exactly what causes these blood clots.
"They refer to it as a rogue response or an abnormal immune response where you have antibodies that are acting inappropriate," said Dr. Roberts. "That's the theory but no one really knows the cause."
Symptoms usually develop within two weeks of getting vaccinated.
Doctors described an unusually severe headache as a warning sign.
"Essentially, you lay down a lot of clots in places you shouldn't, in large veins," said Dr. Roberts. "The most worrisome one of the cerebral sinus vein which is a very large vein in the middle of your head and that's the one that's potentially fatal."
Health officials explained that the benefits still outweigh the risks, even with the new restrictions in place.
"If someone had their J&J vaccine months or a year ago, there is no risk of them developing this type of complication," said Robertson.
Health experts added that rare blood clots are also an issue with the AstraZeneca vaccine which is being used in Europe.
Federal health officials have been recommending the Pfizer and Moderna vaccines, over the J&J since December.