The U.S. Centers for Disease Control and Prevention and Food and Drug Administration are recommending a pause in the use of the single-dose Johnson & Johnson COVID-19 vaccine due to potentially dangerous blood clots. The CDC and FDA said they are reviewing unusual clots in six women, between the ages of 18 and 48, that occurred six to 13 days after vaccination.

As of April 12, more than 6.8 million doses of the Johnson & Johnson vaccine have been administered in the United States. In a joint statement, the FDA and CDC said the clots currently appear to be “extremely rare,” but are “recommending a pause in the use of this vaccine out of an abundance of caution” until the cases are further reviewed. The FDA says the pause is expected to last “a matter of days,” not weeks.

If you have received the Johnson & Johnson vaccine and develop severe headache, abdominal pain, leg pain, or shortness of breath within three weeks after vaccination, you’re advised to contact your health-care provider.

Pennsylvania was expected to receive 20,000 doses of the Johnson & Johnson vaccine, and 2,800 doses were allocated to Philadelphia for the week of April 12, according to the CDC. If you were scheduled for one of those Johnson & Johnson vaccines, you’re likely wondering what you’re supposed to do now. Here’s what we know:

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What to do if you were scheduled for the Johnson & Johnson vaccine

Throughout the region, many locations that were administering the Johnson & Johnson vaccine are temporarily closing or switching to the Pfizer or Moderna vaccine. If you were scheduled for the Johnson & Johnson vaccine and don’t see your location listed below, contact your provider ahead of your appointment.

In Philadelphia, all city-operated and partner clinics have paused the use of the Johnson & Johnson vaccine. The following locations have announced changes:

  • Center City Vaccination Center (FEMA-supported clinic at the Convention Center): Will begin giving out the Pfizer vaccine on April 13, beginning at noon; the clinic will continue administering the Pfizer vaccine for the foreseeable future and will maintain the current 6,000 appointments and walk-ups per day.

  • Esperanza Community Vaccination Center (FEMA-supported clinic at Esperanza): Will close on April 13; starting April 14, the clinic will switch to Pfizer vaccine and will maintain the current 1,000 appointments and walk-ups per day. Folks with appointments today have been notified of their canceled appointment and will receive another notification on how to set up a new appointment soon.

  • Health Department Community Clinics and Health Centers: Will open with normal hours and operations, but will not use Johnson & Johnson vaccine.

  • Philadelphia Fire Department Community Clinics: Will be closed until at least April 19.

  • Health Department and Partner Mobile Teams: Will continue operating, but will not use Johnson & Johnson vaccine.

  • Partner Vaccine Clinics (including Black Doctor’s COVID-19 Consortium, federally qualified health centers, independent and chain pharmacies, hospitals, etc.): Will switch to the Pfizer or Moderna vaccines, if previously administering the Johnson & Johnson vaccine; if unable to make the vaccine switch, the clinics may close; please call ahead if you have an appointment scheduled.

In Bucks County, the mass vaccination site at the former Giant grocery store in Warwick is now closed. “We are waiting to hear more from the state and feds as to how long this pause might last,” said a Bucks County Health Department spokesperson. The site was the only one of its four county-run sites administering the Johnson & Johnson vaccine. People with appointments will be contacted about rescheduling.

» READ MORE: What you need to know about the Johnson & Johnson vaccine and reports of rare blood clots

In Montgomery County, the following county clinics are closed April 13 and 14: Parkside Shopping Center, Willow Grove, Trinity Lutheran Church, Lansdale, and Bethel Community Church of Pottstown, Pottstown. If you were scheduled for an appointment to receive the Johnson & Johnson vaccine at a county clinic, you’ll be contacted by email to reschedule your appointment for a later date.

In Chester County, the Brandywine YMCA clinic in Coatesville and the clinic at the Government Services Center in West Chester are switching to the Moderna vaccine. The Health Department is contacting everyone who has an appointment at those locations to offer the Moderna vaccine instead. The Health Department says it will release an update about plans for later this week and will continue to reach out to people who have Johnson & Johnson vaccine appointments scheduled.

In Delaware County, the Delaware County Community College clinic is temporarily locating and will also switch to Pfizer or Moderna. The county will contact you if you had a scheduled appointment here. The county’s homebound and homeless vaccination programs will switch to Moderna.

In Camden County, county clinics will switch to the Pfizer and Moderna vaccines. If previously scheduled for the Johnson & Johnson vaccine, you don’t need to reschedule and can go to your appointment as planned.

The Pennsylvania Department of Health has notified vaccine providers to pause administering doses of the Johnson & Johnson vaccine until at least April 20. The New Jersey Department of Health has also paused the administration of the Johnson & Johnson vaccine across all vaccination sites in the state.

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