TAMPA, Fla. -- The medical community is working to find out more about COVID-19 antibodies, like what kind of protection they offer and for how long. 

A letter published Tuesday by the "New England Journal of Medicine" ends with a cautionary note. Doctors with the David Geffen School of Medicine wrote that immunity against COVID-19 may not be long-lasting for patients with mild cases. They point out it's this group that makes up the majority of those with the virus. 

"As far as reinfections go, is this something that we're seeing more of?" "Well, we are hearing anecdotal reports of people getting reinfected," Dr. Michael Teng, USF Internal Medicine Department Associate Professor. 

However, Dr. Teng said he expects those instances will be rare. 

The Geffen researchers said they observed 34 coronavirus patients with mild symptoms for three months. They found what they called "rapid decay" of the antibodies, noting they seemed to break down more quickly than those associated with SARS, another coronavirus. 

"We have to understand that anytime we look at these results, it's based on a certain population of people, and these are really the first results that are coming out," he said. 

Dr. Teng said it's normal to see antibody levels drop once any kind of infection clears up. 

"It doesn’t go down to zero. It actually comes down to sort of a baseline, and that baseline is really what we’re trying to look at when we do vaccine studies, because what does that baseline level of antibody that are needed in order to protect you from a second infection?” Teng said. 

Researchers wrote that vaccine durability is one area in which their results may signal a need for caution. 

Doctors also say more studies in this area will be needed.