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HIGHLANDS RANCH, Colo. (KDVR) — When Alexis Smith of Highlands Ranch came down with terrible flu symptoms and an ear infection in February it never occurred to her or her doctors that she might have COVID.

“The breathing was the biggest thing, everything was exhausting. I couldn’t go more than five feet without having to stop take a deep breath of air and overall the most irritating thing was the no one could tell me what was wrong,” Smith said.

It wasn’t until she tested positive for COVID-19 antibodies in July that her belated suspicions were confirmed.

“I thought I was invincible,” Smith said, who figured the good thing about already having had COVID-19 was that she now enjoyed immunity. But those feelings didn’t last long. In early October, the 28-year-old was re-tested and this time her antibody test came back negative.

“Well now I’m thinking I might not be invincible and that stinks. I’m hoping I don’t get it again,” Smith said.

It’s certainly possible according to Dr. Cory Hussain, an infectious disease expert at Denver Health Medical Center who said just at his hospital alone, “We’ve had four cases of reinfection.”

“The second infection that happens generally tends to be asymptomatic though, patients don’t tend to get as sick,” according to Dr. Hussain.

This was a notable exception that made national news last week though when it was determined a 25-year-old Nevada man suffered more severe symptoms after becoming re-infected with COVID-19.

Health experts are now learning COVID antibodies can decay in a matter of months. 

“There are these reports where antibodies disappear after a few months,” said Dr. Thomas Jaensich, an associate professor at the Center for Global Health, who’s based at the Colorado School of Public Health.

“I think that we all should not at this point think that having had COVID or having antibodies is a get out of jail card,” when it comes to getting sick again according to Dr. Jaensich.

He pointed out that even if someone like Alexis Smith gets a second case with mild or no symptoms, she could still pass COVID onto some else which is the last thing she told FOX31 she wanted to do, “Cause it was the one of the worst experiences in my life.”

Medical experts told the Problem Solvers the fact that antibodies may only last three to six months suggests a COVID vaccine may be like the Flu vaccine, a new dose needed each year.

“And even with the Flu vaccine we know once you get the Flu vaccine it doesn’t stop you from possibly getting the influenza but if you do, your symptoms are extremely mild. That might be the case even with the COVID vaccine. It might not stop you from getting the COVID infection but the chances are you might not get sick at all,” said Dr. Hussain.

A study published last week in the journal Immunity found most people who recover from COVID-19 are believed to be protected against infection for at least five to seven months.