Missouri joined other states Tuesday and suspended the use of Johnson & Johnson's COVID-19 vaccine as federal agencies look into six cases in which women who received the single-dose drug developed blood clots.

Dr. Randall Williams, director of the state's Department of Health and Senior Services, said in a news release that Missouri was taking the step out of “an abundance of caution." He made the announcement after the Centers for Disease Control and Prevention and the Food and Drug Administration advised pausing the use of the drug while they investigate the six cases.

“We anticipate having more information shortly to make further decisions about overall vaccine distribution in light of this new development and will continue to update citizens who have been vaccinated with the J&J vaccine after the advisory committee meets at the federal level tomorrow,” Williams said.

More than 6.8 million doses of the J&J vaccine have been administered in the U.S., the vast majority with no or mild side effects. In the six cases, the clots occurred in veins that drain blood from the brain and the patients also had low platelet counts. All six were in women between the ages of 18 and 48, including one who died.

St. Louis County has administered about 1,800 of J&J doses, primarily to people who were homebound, and it had planned to use it to vaccinate the homeless, Dr. Faisal Khan, the director of the county’s health department, said during a video call with reporters.

He said the county was reaching out to all of the people who got the J&J doses to see if any were experiencing adverse reactions aside from the normal chills and fever that many patients get soon after being immunized, including with other companies' COVID-19 vaccines.

He said the county had received a relatively modest amount of the J&J vaccine and would simply switch to only using the two-dose versions made by Pfizer and Moderna. That would allow it to continue its vaccine rollout largely as planned, although he acknowledged there would be some hassles because they require two doses three or four weeks apart.

“The convenience afforded by the Johnson & Johnson vaccine was that it was a one shot and you are done kind of deal so you would only have to visit a particular individual once," he said.

He said his “greatest worry" is that the investigation could add to some people's hesitancy to get vaccinated. Despite expanding eligibility to everyone age 16 or older in the state, vaccine demand has slowed even though cases have been rising.

The St. Louis health department on Monday reported that the city has seen an increase over the past two weeks in new COVID-19 cases, with the seven-day average increasing to 28, from 20. Meanwhile, mass vaccinations at The Dome at America’s Center in downtown St. Louis haven’t been able to use all the doses they’ve been allotted.

“This is not a cause for people to hesitate to get the shots that are available to them," Khan said. “This is simply the regulatory agencies and the premiere public health care agencies intervening to make sure that we minimize the risk even further.”

The Kansas City Health Department requested the J&J vaccine but has not received any, spokeswoman Michelle Pekarsky told The Kansas City Star.

Platte County's health department, meanwhile, asked anyone who was scheduled to get the J&J vaccine to reschedule.

And the vaccine's suspension caused problems for people who were scheduled to get it at Kansas City-area Sun Fresh, Hen House and Price Chopper stores. Amanda Applegate, immunization coordinator for Balls Food, which owns the stores, said people with canceled J&J appointments were being advised to sign up for either the Moderna or Pfizer vaccine, as they still have appointments openings for the two-dose shots.

“A vaccine is still the best way to combat this virus,” Applegate said.