Anthony Fauci says people who recover from the coronavirus should be immune through at least September. But some scientists worry that not all patients develop antibodies.

• Dr. Anthony Fauci says people who recover from the coronavirus will likely be immune should a second wave of infection spread in the early fall.
• He explained that because the virus has not mutated much, people who develop immunity will likely maintain it at least for the next few months.
• Preliminary studies about coronavirus immunity and antibodies have shown that most, but not all, recovered patients develop antibodies.
• Visit Business Insider’s homepage for more stories.

Dr. Anthony Fauci offered some insight into crucial questions about coronavirus immunity during an interview on Wednesday.

In a livestreamed conversation with Journal of the American Medical Association editor Howard Bauchner, Fauci said it’s unlikely that people can get the coronavirus more than once.

“Generally we know with infections like this, that at least for a reasonable period of time, you’re gonna have antibodies that are going to be protective,” he said.

Fauci added that because the virus doesn’t seem to be mutating much, people who recover will likely be immune should the US see a second wave of spread in the fall.

"If we get infected in February and March and recover, next September, October, that person who's infected - I believe - is going to be protected," he said.

A second spike in the US's caseload is a real threat, Dr. Deborah Birx warned on Wednesday. Birx, the White House coronavirus response coordinator, said Americans are at risk of a "very acute second wave" of coronavirus infections if they don't continue social distancing.

Developing immunity to the coronavirus

One reason the coronavirus has spread so quickly is because it's new, so none of our bodies have encountered it before. The immune system has to develop antibodies - proteins that fight a specific antigen - before we gain protection against a virus.

Generally, once your body has antibodies to fight off a particular disease, you can't get it again. That's why someone who had chickenpox or got the vaccine won't get the disease twice. However, with viruses that mutate - such as the common cold or seasonal flu - antibodies people build up against one strain aren't effective against others. Plus, some types of antibodies weaken over time.

Fauci said it's possible that could happen with the coronavirus as well, but it's unlikely.

"If a person gets infected with coronavirus A, and then gets reinfected with a coronavirus, it may be coronavirus B," Fauci said. "But right now, we don't think that this is mutating to the point of being very different."

Over 315,000 people worldwide have recovered from the coronavirus (likely more, given that many mild and asymptomatic cases are not reported in official counts). Given that a third of the world is under some kind of lockdown, those who have recovered could potentially emerge and return to work first.

"Those are the people, when you put them back to particularly critical infrastructure jobs, that you worry less about them driving an outbreak than those who are antibody-negative and very likely have never been exposed," Fauci said.

Lingering questions about coronavirus immunity

Scientists still don't know how long immunity to the coronavirus lasts, since it has only been around since November or December.

"It hasn't been looked at as carefully as we would have liked now to have looked at it," Fauci said of the question of immunity.

Some early research suggests that not all recovered patients develop coronavirus-neutralizing antibodies to the same degree. According to a report from Chinese scientists that has not yet been peer-reviewed, about 10 of 130 participants studied did not develop neutralizing proteins. This suggests they might have a higher risk of reinfection.

As scientists race to develop a vaccine for the coronavirus, these findings could have implications about its potential effectiveness.

"What this will mean to herd immunity will require more data from other parts of the world," Huang Jinghe, the leader of the Chinese research team behind the report, said on Tuesday, according to the South China Morning Post.

If the virus does not always produce an antibody response, a vaccine might not always create immunity, either.

"Vaccine developers may need to pay particular attention to these patients," Huang added.

Some reports also describe people who've recovered from an infection then tested positive again later. This was the case for a Japanese tour guide who got sick, got better, then tested positive for the coronavirus three weeks later. Doctors aren't sure if she was reinfected or had not fully recovered from the first infection.

Earlier this week, the Korean Center for Disease Control reported that 51 patients in South Korea retested positive for the virus, according to the Yonhap News Agency. Jeong Eun-kyeong, Director-General of the Korean CDC, said the virus was likely "dormant" then "reactivated." The tests were conducted within a "relatively short time" after the patients were released, he said, so it's unlikely the patients got reinfected. Plus, PCR tests for active coronavirus infections can be inaccurate.

More research is needed to determine whether virus can indeed go dormant.

Morgan McFall-Johnsen contributed reporting.