April 14, 2021 -- A pause in the use of Johnson & Johnson’s COVID-19 vaccine will not hamper the country’s immunization efforts, White House officials said Wednesday during a COVID-19 briefing.

“I want to be clear that this announcement will not have a significant impact on our vaccination program,” said White House COVID-19 Response Team Coordinator Jeff Zients. “The Johnson & Johnson vaccine makes up less than 5% of the more than 190 million reported shots in arms in the U.S. to date.”

The FDA and CDC on Tuesday recommended placing a hold on giving the Johnson & Johnson vaccine after reports of blood clots in patients who had received the shot.

Zients said that while there may be short-term disruption while vaccination sites adjust to the change, there will be no serious effects on distribution. Pfizer CEO Albert Bourla, PhD, said late Tuesday the delivery of doses will be sped up in light of the Johnson & Johnson news.

The six reported blood clot cases happened in women ages 18-48, and symptoms arose 6 to 13 days after they received the vaccine. More than 6.8 million doses of the Johnson & Johnson vaccine have been given.

The CDC’s Advisory Committee on Immunization Practices is meeting today to discuss potential updates to its Johnson & Johnson’s vaccine recommendations, CDC Director Rochelle Walensky, MD, said during the briefing. She said there may be more cases of blood clots than officials are aware of.

“Right now we believe these events to be extremely rare, but we're also not yet certain we've heard about all possible cases, as this syndrome may not be easily recognized as one associated with the vaccine,” she said.

She assured those who have received the vaccine that their risk of blood clots is low.

“I know the information we have presented may be very concerning to Americans, especially those who have already received the Johnson & Johnson vaccine. For people who have received the vaccine more than a month ago, the risk of a blood clot is exceptionally low,” Walensky said. “For people who received the vaccine recently, meaning in the last few weeks, they should be aware of their symptoms and immediately seek medical assistance with any symptoms of concern.”

But, she said, “even in this group, these events are extremely rare.”

Walensky said to look out for symptoms including severe headache, belly pain, leg pain, and shortness of breath.

Top COVID-19 expert Anthony Fauci, MD, said the pause should not add to vaccine hesitancy -- rather, it should increase confidence in the monitoring process.

“When I go out and try to counter the issues of hesitancy, a substantial proportion of hesitancy is centered around the concern that the vaccines might not be safe,” he said. “The fact that following the [emergency use authorization], we have continued to follow very carefully the possibility of adverse events is the other side of the coin of hesitancy. It should reinforce in those individuals [who are hesitant] how we take safety so seriously.”