A new study of 30,000 COVID-19 patients suggests that the antibodies people produce to fight off the virus last longer than previously believed.
The finding should help vaccine makers as well as researchers who have been trying to determine whether COVID-19 survivors can become reinfected.
“Some (studies) reported declines in antibodies the first few weeks and first months and that isn’t what we have seen,” said Ania Wajnberg, lead author of the new study and medical director of Mount Sinai’s clinical antibody testing program.
“We see a slight decline, but overall a stable level.”
The paper, published this week in the journal Science, reported that most people with mild to moderate COVID-19 produce antibodies that are still effective five months after the onset of symptoms.
Roughly 92% of the patients produce sufficient antibody levels to continue fighting the new coronavirus.
Past studies found that antibody levels seemed to drop off faster. The other studies focused on antibodies produced in response to a viral protein known as NP. But it turns out NP may not be a good measure because it has membranes that shield it from the antibodies created by our immune system.
The team at Mount Sinai in New York focused instead on the infamous Spike protein, which allows viral cells to attach themselves to human cells.
After measuring antibody response in the entire group of 30,000 COVID-19 patients, scientists then followed a smaller subset. This second group consisted of 121 patients, who went on to donate plasma to help others fight COVID-19.
When researchers measured antibody levels in the group of 121 they found only a slight drop between three months and five months after symptoms. There was a larger decline at about 148 days, but the antibody levels were still high enough to neutralize the virus. Wajnberg said the Mount Sinai team plans to follow the 121 plasma donors for at least a full year.
The study suggests that vaccine makers should target the Spike protein because it spurs a much stronger immune response than the NP protein.
“I think it’s an important question to look at. It will help us determine what the chances are of people being reinfected,” said Nasia Safdar, medical director of infection control at UW Health.
Safdar said learning how long antibodies endure and remain effective will also help solve the intriguing question of whether or not people can become reinfected by the new coronavirus.
Safdar said UW Health has had a handful of cases that may have involved reinfection but stressed “it’s hard to prove.”
Doctors cannot be sure whether a patient who comes back with COVID-19 has been infected a second time or still has remnants from the first infection.