CHICAGO (CBS) — The city of Chicago is putting several vaccination programs on hold, including shots for homebound seniors, after the CDC and FDA recommended a “pause” in the use of the Johnson & Johnson/Janssen coronavirus vaccine while they investigate six cases of “a rare & severe type of blood clot” in people who received the vaccine.

The Chicago Department of Public Health on Tuesday announced it was following federal guidance to pause administering the Johnson & Johnson vaccine while the feds complete their review. CDPH Commissioner Dr. Allison Arwady said she expects a drop in vaccination rates as a result of the pause.

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“I expect not just in the city but across the country, we’ll see some drop in the rate of vaccinations as a result of this,” Arwady said Tuesday afternoon during a regular Q&A session on Facebook.

Arwady noted the single-dose Johnson & Johnson vaccine makes up a much smaller portion of the vaccine supply than the two-dose Pfizer and Moderna vaccines, which are not affected by the pause.

“This has not shaken my confidence in the safety and efficacy of the vaccination program broadly in the U.S.,” Arwady said.

However, the city is putting a number of its vaccination programs on hold because they rely on the Johnson & Johnson vaccine, including the city’s program to bring vaccines to homebound seniors, the city’s vaccination site at O’Hare International Airport, a vaccination clinic for restaurant workers, and the city’s new mass vaccination site at Chicago State University.

“I expect this to be a relatively short-term pause while the scientists look at the data and then make some recommendations,” Arwady said.

At Chicago State University, the city will immediately switch from the Johnson & Johnson vaccine to the Pfizer vaccine. While no appointments had been scheduled for Tuesday, Arwady said all appointments on Wednesday and going forward will remain as scheduled, using the Pfizer vaccine.

The employer-based vaccination program at O’Hare and a special vaccination event at Midway International Airport have been postponed for now, Arwady said.

The city’s program to vaccinate homebound seniors will also be put on hold at least until Monday. Arwady said about 5,000 seniors have registered for the program, and the city has already contacted everyone who has scheduled an appointment to inform them what’s happening.

Chicago Federation of Labor vaccination clinics for eligible union workers on Thursday and Friday have been delayed at least until next week, as has an Illinois Restaurant Association vaccination event in Albany Park, Arwady said.

Sam Toia, president of the Illinois Restaurant Association, expressed disappointment, but understanding, at the developments with the fully-booked vaccination event scheduled now having to be rescheduled.

“We had over 600 people that were scheduled to get the vaccine the J&J vaccine,” Toia said. “Obviously, I was disappointed, but the health of our team members is always number one. Again, this is postponed.”

More than 600 hospitality workers had been expected at the Illinois Restaurant Association event.

“We were starting a waiting list in case people canceled,” Toia said. “We’re hoping to have more vaccines and make sure and have more programs across the city to get hospitality workers vaccinated if they want the vaccine.”

A mobile vaccination program using a CTA bus to reach seniors in neighborhoods with low vaccination rates also has been put on hold. That program had stops scheduled this week in South Shore and West Englewood. Those programs, as well as the homebound programs, rely on Johnson & Johnson because of the less-rigorous cold storage requirements.

Arwady said the United Center mass vaccination site was scheduled to switch to the Johnson & Johnson vaccine on April 20, and because its supply comes directly from the federal government, the city is still waiting to hear from the Federal Emergency Management Agency on their plans for the United Center going forward.

“We will need to hear from them about timing and next steps there,” Arwady said Tuesday afternoon at a COVID-19 briefing at City Hall.

Meantime, appointments for Johnson & Johnson vaccines at the United Center will be paused while the city waits to learn more from the feds.

A change to the single-dose Johnson & Johnson vaccine at the United Center site, announced just two days ago, was not set to take effect until Tuesday, April 20.

Arwady said Tuesday that the Johnson & Johnson vaccination “pause” will not impact operations here at the United Center this week – because right now, they are still administering the Pfizer vaccine.

Next week’s vaccinations are to be determined.

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Cook County said vaccinations at their Tinley Park mass vaccination site have also been halted.

Arwady said the timing of the pause in Johnson & Johnson vaccines is unfortunate, particularly given that the state of Illinois on Monday expanded eligibility for the vaccine to everyone age 16 and older, and the city of Chicago is scheduled to follow suit next Monday.

“This is a hit, no doubt about it,” Arwady said.

However, Arwady stressed that people who have recently received the Johnson & Johnson vaccine should not be overly concerned, given how rare the blood clot cases have been. Only six cases of severe blood clots have been reported among the more than 6.8 million doses of the single-dose vaccine that have been administered across the country.

“You should not be severely worried at all if you got the Johnson & Johnson vaccine,” Arwady said.

Arwady said she worries about the impact the pause could have on vaccine hesitancy across the city. But she is encouraging Chicagoans to keep their Pfizer and Moderna appointments.

“I am concerned, because I know people will have concern when they hear this,” Arwady said. “Getting Chicago past COVID; getting the U.S. past COVID, means getting us vaccinated.”

Anyone who received the Johnson & Johnson vaccine within the last couple of weeks should “be aware to look for any symptoms,” said Anne Schuchat, principal deputy director of the CDC.

Those who develop severe headache, abdominal pain, leg pain or shortness of breath within three weeks after getting the vaccine should contact their health care provider and seek medical treatment, she said.

Schuchat said the risk is “very low” for people who received the Johnson & Johnson vaccine more than a month ago.

Deerfield-based Walgreens released a statement regarding the halt on putting out more Johnson & Johnson vaccine:

Following today’s recommendation from the FDA and CDC for a pause in the use of the J&J vaccine out of an abundance of caution, we are immediately suspending the administration of the J&J vaccine at our stores and off-site clinics and are awaiting further guidance. We are reaching out to patients with scheduled appointments and rescheduling vaccinations from other manufacturers, as supply allows. We will continue to work closely with the FDA and CDC and, as always, the health and safety of our patients and customers is our highest priority.

The handful of cases the FDA and CDC are investigating occurred in women and involved a blood clot called cerebral venous sinus thrombosis, which was seen alongside low levels of blood platelets, according to their statement. Symptoms were seen 6 to 13 days after vaccination in the women, who were between the ages of 18 and 48.

“Treatment of this specific type of blood clot is different from the treatment that might typically be administered. Usually, an anticoagulant drug called heparin is used to treat blood clots. In this setting, administration of heparin may be dangerous, and alternative treatments need to be given,” they said.

The agencies said the “adverse events” seem to be extremely rare, but that the pause is important so that health care providers can be made aware of the reactions and properly recognize and manage the cases, given the unique treatment required.

“I do think it is the right decision while the teams at the federal level investigate this data,” Arwady said.

The CDC will convene a meeting of the Advisory Committee on Immunization Practices (ACIP) on Wednesday to review the six blood clot cases. The FDA will then review that analysis as it also investigates the cases.

“It’s pretty unusual to have blood clots in combination with low platelets,” Arwady said. “These people were getting blood clots not just in their leg, but they were getting blood clots … it was draining from their brain, and that can be really serious.”

Arwady said she expects the ACIP likely will make more recommendations regarding the Johnson & Johnson vaccine on Wednesday.

She said the pause in administering the Johnson & Johnson vaccine doesn’t mean it won’t ever be used again to inoculate people against COVID-19.

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“They will want to understand was there something that these women had in common that maybe made them at more risk for this? We don’t know for sure that it was related to the vaccine, but having these two rare events together was more than you would expect,” Arwady said. “This is why we have the really good sort of safety and monitoring protocols in place at the federal level.”

Megan Hickey