• One leading virus expert said that, for this reason, "there's not much we can do until there's a vaccine" to create herd immunity.
  • Even if and when coronavirus vaccines prove successful, they may require booster shots.
  • Visit Business Insider's homepage for more stories .

Roughly six months into the coronavirus pandemic , emerging evidence is starting to suggest that people who've been infected with this virus could still be susceptible to getting it again.

"We know that from other coronaviruses, from regular human, common cold coronaviruses, that you probably get immunity for some time once you're infected," Florian Krammer, a vaccine scientist and virus expert at the Icahn School of Medicine at Mount Sinai in New York, told Business Insider. "But it's not perfect."

Krammer says that a person's second coronavirus infection could be milder, or even asymptomatic where they display no outward signs of sickness at all. But his assertion backs up what new data around the world is also starting to suggest: that the body may, after a few months, start to forget it had the disease caused by the novel coronavirus, COVID-19.

This prospect of a potential for waning coronavirus memory in our immune systems may make it more difficult to rid the world of this virus, permanently, especially without a vaccine.

Growing evidence immunity may not last

Research published in the medical journal The Lancet earlier this month suggests that people who had the coronavirus in Spain, and subsequently developed antibodies to it producing the proteins thought to possibly help protect against reinfection are seeing their antibody levels wane, just months after an illness.

Likewise, new research out of the UK on Saturday (which has yet to be peer-reviewed) also suggests that a person's coronavirus antibody levels tend to peak a few weeks after an infection, before gradually declining, and in some cases, disappearing entirely.

This data suggests that the prospect of herd immunity the idea that enough people in a given community could develop immune protection against a virus, halting its spread and shielding the vulnerable from infection is going to require more than just natural-borne illnesses.

"There's not much we can do until there's a vaccine," Krammer said. "With a vaccine, you're able to reach herd immunity very quickly."

'Are the antibodies useful?'

There is no solid evidence, yet, that anyone has been reinfected with the novel coronavirus , but this threat of waning antibody levels lends more weight to the idea that it could happen , which may make it harder for the world to stamp out the coronavirus, and could make producing coronavirus vaccines an even trickier task, too.

"We need to figure out how this works for this coronavirus, are the antibodies useful?" Krammer asked. "The answer is probably yes, but then the critical answer is how much antibodies do you need, in order to be protected?"

Dr. Anthony Fauci, director of the US' National Institute of Allergy and Infectious Disease, agrees that this is one of the top mysteries scientists have yet to solve about the coronavirus, and the answer to it has consequences for the success of any eventual vaccines.

"Will we get the body to induce a durable response that can protect you?" Fauci asked Monday, during a livestream chat with the dean of Stanford Medical School. "Whether that response is following recovery from natural infection and/or induction of immunity by a vaccine, is it possible to have durable, effective immunity? I think it is, but it's still an unanswered question that we need to prove."

It's possible that people will need to be administered a few courses of a vaccine, or be topped up from time to time with booster shots , in order to make any eventual coronavirus protection long-lasting.

NOW WATCH: 6 months of the coronavirus pandemic in the United States, reviewed in 6 minutes

See Also: