As The Epoch Times' Zachary Stieber reports, the people reporting the negative effects reported them through V-safe, a smartphone application. The tool uses text messages and web surveys to provide personalized health check-ins and allows users to quickly tell the CDC if they are experiencing side effects.

The CDC and Pfizer, which produces the vaccine with BioNTech, didn’t respond to request for comments.

The information was presented by Dr. Thomas Clark, a CDC epidemiologist, to the Advisory Committee on Immunization Practices, an independent panel that provides recommendations to the agency, on Saturday.

The CDC said that 272,001 doses of the vaccine were administered as of Dec. 19. That means most people who were vaccinated did not experience negative effects.

The CDC has identified six case reports of anaphylaxis, or severe allergic reaction, that occurred following vaccination with the new vaccine, Clark reported. Other case reports were reviewed and determined not to be of anaphylaxis.

In an update on Friday, the agency stressed that anyone who has ever had a severe allergic reaction to any ingredient in a COVID-19 vaccine should not get that vaccine. People with severe allergic reactions to other vaccines should consult their doctor about getting the new vaccine while those with a history of anaphylaxis not related to vaccines “may still get vaccinated.”

“CDC recommends that people with a history of severe allergic reactions not related to vaccines or injectable medications - such as allergies to food, pet, venom, environmental, or latex - may still get vaccinated," the CDC said.

"People with a history of allergies to oral medications or a family history of severe allergic reactions, or who might have a milder allergy to vaccines (no anaphylaxis) - may also still get vaccinated.”

Anyone who experiences anaphylaxis after getting the first vaccine should not get the second shot, the CDC said. COVID-19 vaccines are meant to be given across two doses, spaced about three weeks apart.

At least five healthcare workers in Alaska experienced adverse reactions after getting the Pfizer vaccine, the Anchorage Daily News reported. One of two experiencing adverse reactions at the Bartlett Regional Hospital required treatment at the hospital for at least two nights.

An Illinois hospital halted vaccinations after four workers suffered adverse reactions.

Dr. Peter Marks, the director of Food and Drug Administration’s Center for Biologics Evaluation and Research, told reporters in a call on Thursday night that the agency is working with the CDC, and colleagues in the United Kingdom, on probing the allergic reactions.

“We’ll be looking at all of the data we can from each of these reactions to sort out exactly what happened. And we’ll also be looking to try to understand which components of the vaccine might be helping to produce them,” he said.

A container of 5 doses of COVID-19 vaccine sits on a table at Roseland Community Hospital in Chicago, Ill., on Dec. 18, 2020. (Scott Olson/Getty Images)

Noting that he was speculating, Marks said it’s known that polyethylene glycol - a component present in both the Pfizer vaccine and one from Moderna that regulators approved earlier in the day - can be associated, uncommonly, with allergic reactions.

“So that could be a culprit here. And that’s why we’ll be watching very closely,” he said. “But we just don’t know at this point.”

Both vaccines have “systemic side effects,” which are “generally mild,” Marks said.

They go away after a day. According to the FDA website, the most commonly reported side effects include tiredness, headache, muscle pain, and chills. The agency said they go away after several days.

One volunteer in Pfizer’s late-stage clinical trial experienced an allergic reaction. Two people in Moderna’s phase 3 clinical trial experienced anaphylactic reactions, the company said during a meeting on Thursday. But the data showed the benefits outweigh the risk, FDA officials said, as they granted emergency use authorization to the vaccines about seven days apart.

People who get a COVID-19 vaccine should be monitored for at least 15 minutes after getting vaccinated, according to the CDC.

If someone experiences a severe allergic reaction against getting a COVID-19 vaccine, vaccination providers are supposed to provide rapid care and call for emergency medical services. The person should continue to be monitored in a medical facility for at least several hours.