U.S. health officials recommended Thursday that most Americans should receive the Pfizer or Moderna vaccines instead of the Johnson & Johnson shot that can cause rare but serious blood clots. 

The clotting problem has caused nine confirmed deaths after J&J vaccinations — while the Pfizer and Moderna vaccines don't come with that risk and also appear more effective, according to advisers to the Centers for Disease Control and Prevention.

The panel recommended the unusual move of giving preference to the Pfizer and Moderna vaccines, and Thursday night the CDC's director, Dr. Rochelle Walensky, accepted the panel's advice.

Philadelphia Health Commissioner Dr. Cheryl Bettigole responded to the CDC’s comments in a written statement on Thursday, stating that those who got the J&J vaccine more than two weeks ago who haven’t experienced any symptoms should be fine.

“It’s important to remember that no one who experienced the blood clotting side effect did so more than two weeks after they got their Johnson & Johnson vaccine, so if it’s been longer than that, you should be okay,” Dr. Bettigole said. “If you recently received a first dose of Johnson & Johnson vaccine within the last four weeks, seek immediate medical care if you experience certain symptoms.”

Those symptoms include the following: 

• Severe headache 
• Backache 
• New neurologic symptoms 
• Severe abdominal pain 
• Shortness of breath 
• Leg swelling 
• Tiny red spots on the skin (petechiae) 
• New or easy bruising 

Dr. Bettigole also detailed the differences between the vaccines. 

“The Johnson & Johnson vaccine works differently than either the Pfizer or Moderna vaccine, and this blood clotting side effect has not been seen in people who got those vaccines,” she wrote. “I still strongly recommend that everyone who is eligible get every dose of COVID vaccine that they are eligible to receive as soon as possible. People who are younger than 60 should seek out either Pfizer or Moderna vaccine, rather than J&J.”

Dr. Bettigole also reiterated the importance of still being fully vaccinated. 

“Even with this new development, COVID vaccines are our best defense against severe COVID disease,” she wrote. “They can reduce your risk of contracting and spreading COVID, and are much more likely to keep you from experiencing severe symptoms.”

During a press conference on Wednesday, which marked the one year anniversary of the first COVID vaccines arriving in Philadelphia, health leaders warned that the city was entering the most dangerous time in the pandemic since last winter. 

During the presser, Dr. Bettigole said that 220,000 people in the city still aren’t vaccinated. She also said about 91 percent of the most recent COVID cases are people who are unvaccinated. Finally, she revealed that as of Tuesday, 347 people in Philadelphia were hospitalized because of COVID. 

Dr. Bettigole urged residents not to have large indoor gatherings during the holidays and to avoid gatherings with other families. 

“Please do not hold or attend holiday parties indoors,” she said. “It’s just too dangerous. Instead, profess your brotherly love and sisterly affection by wearing your mask, avoiding crowded indoor spaces, and staying home if you’re sick.”

On Monday, city officials announced that Philadelphia will require proof of vaccination to eat indoors in restaurants or drink inside bars -- or to enter any indoor space that sells food and drink -- starting Jan. 3. 

Initially, a recent negative COVID-19 test will also be accepted. However, after Jan. 17, negative COVID-19 tests will no longer be accepted for most patrons and vaccines will be required. Restaurant workers also must be vaccinated.

Children younger than 5 or those with valid medical or religious exemptions will be able to show a recent COVID-19 test to go inside.