CHICAGO (CBS)– Pfizer vaccinations resume tomorrow at Advocate Condell Medical Center in Libertyville, after the hospital suspended administering the vaccine Friday night when four employees had varying reactions.

Advocate Aurora Health said they conducted a thorough review and didn’t find a problem with the vaccine batch, but out of an abundance of caution, they will increase the post-vaccine evaluation time for their staff from 15 to 30 minutes

READ MORE: Mother, 2-Year-Old Daughter Carjacked In Wicker Park

CBS 2’s Marissa Parra reports four Condell Medical Center employees had allergic reactions since vaccinations began on Thursday. Officials said three were mild reactions, with one described as a “severe allergic reaction” known as anaphylaxis.

Due to privacy laws, we don’t know anything about if that person had a prior history of allergies, but we do know they are home and doing well.

After thousands of healthcare workers across Illinois got their first dose of the Pfizer COVID vaccine this week, Condell Medical Center hit pause Friday night when a handful of employees had differing reactions. Three were mild, one described as more severe by health officials.

“A fourth was a more severe reaction characterized as anaphylaxis. That person was treated, observed in the hospital overnight,” said Dr. Robert Citronberg, executive medical director of infectious disease and prevention at Advocate Aurora Health.

That fourth person was released from the hospital on Saturday and said to be doing well, but the question remains why the four reactions at one hospital?

“We’ve given now approximately 6,000 vaccinations throughout our entire system in Illinois and Wisconsin, and we had four of these such reactions at Condell. So the immediate concern was ‘Is there something wrong with that batch of vaccines?’” Citronberg said.

Advocate Aurora Health consulted the U.S. Centers for Disease Control and Prevention, as well as state and local health departments, who eventually came to the conclusion that the batch couldn’t have been bad, because parts of that same batch were given to other hospitals where no reactions were reported.

“It is normal for some folks to sometimes have what we call vasovagal reactions. … It can happen with bloodwork too,” said Dr. Marina Del Rios, a UIC emergency room doctor who was the first person in the state to receive a COVID vaccine. “Someone sees a needle approaching them. Sometimes people get a little bit of palpitations, a little bit of tingling.”

Del Rios said, while we don’t know the specifics of these reactions, side effects from the vaccine in general have proven rare.

READ MORE: Dollar General Hiring 20,000 Workers Across The Country

“For the most part, it’s some soreness, maybe some fatigue. Some people can get some people get low-grade fevers,” she said. “But, again, they’re very rare.”

Doctors say what’s less rare are the effects of COVID-19.

“Those that survive, a lot of people are left with long-term side effects,” Del Rios said. “Scarring of the lungs. Some people are left with stroke-like symptoms.”

Citronberg emphasized it’s all about context.

“We’re going to have occasional reactions, there’s no doubt about it, and I feel that we’re adequately prepared to handle those if and when they occur,” he said.

“The vaccine is our only way out of the pandemic at this point,” he added. “Without a vaccine, the pandemic could go on easily for two years, three years, or longer.”

To put things into a wider perspective, remember these are four reactions out of roughly 6,000 vaccinations for Advocate Aurora Health.

The CDC said, on a national scale, only 6 out of over 272,000 shots of the Pfizer vaccine have resulted in an allergic reaction. Hours ago, they updated their COVID vaccine guidance to underscore this: if you have a history of severe allergic reactions, it’s a good idea to talk to your doctor about options ahead of getting the vaccine.

Condell Medical Center said they have 120 hours to use the Pfizer vaccine once a vial is thawed, and the vaccines they weren’t able to administer today are still in that 120-hour period, meaning none were lost.

MORE NEWS: Video From Police Shooting That Killed Adam Toledo To Be Released On Thursday, COPA Says

Also From CBS Chicago: