The White House on Tuesday sought to reassure the public after health officials called for a pause on the use of the Johnson & Johnson COVID-19 vaccine because of rare cases of blood clots in vaccinated people.

Anthony Fauci, the government’s top infectious disease expert, and Jeff Zients, the White House coordinator for the COVID-19 response, were added to the daily press briefing on Tuesday.

Zients argued that the pause would not lead to a major hit to the U.S. vaccination effort. 

“Let me start by saying this announcement will not have a significant impact on our vaccination program,” he said. “The J&J vaccine makes up less than 5 percent of the more 190 million reported shots in arms in the United States to date.”

There are 28 million doses of the other two vaccines, from Pfizer and Moderna, going out this week. 

“We have more than enough supply of Pfizer and Moderna vaccines to continue the current pace of about 3 million shots per day,” Zients said. 

While Johnson & Johnson doses were a fairly small part of the U.S. vaccination effort so far, there is also the larger question of whether the news will affect overall public confidence in the vaccines, given that vaccine hesitancy in some areas was already a concern. 

“Look, hesitancy amongst a group of people is a challenge and we need to be addressing it and we are,” Zients replied when asked directly by a reporter: “Do you think the announcement of this pause will increase or decrease vaccine hesitancy?”

Both Zients and Fauci sought to argue that the Food and Drug Administration (FDA) and Centers for Disease Control and Prevention (CDC) taking the action that they did showed that the system is working and safety checks are in place. 

“The fact that a pause was done, I think is just a testimony to how seriously we take safety and why we have an FDA and a CDC that looks at this very carefully and hopefully will resolve it within days to weeks,” Fauci said. “I think it’s a very strong argument for safety actually.”

The pause was initiated because of very rare cases of blood clots, just six cases out of about 7 million Johnson & Johnson vaccine doses administered have been reported so far. No serious safety problems have been reported with the Pfizer or Moderna vaccines. 

For people who already got the Johnson & Johnson vaccine, Fauci reassured: “I would tell them to just, first of all, don't get an anxiety reaction because remember, it’s less than one in a million.”

“However having said that, pay attention, do you have symptoms? Headache, shortness of breath, chest discomfort,” he added. People with those symptoms, or leg pain or abdominal pain, within three weeks of vaccination with the Johnson & Johnson vaccine, should contact their doctor, the FDA said.