Anthony Fauci (front), director of the US National Institute of Allergy and Infectious Diseases(NIAID), attends a press conference on the coronavirus at the White House in Washington D.C., the United States, on March 2, 2020. (Xinhua/Liu Jie)

 
The US government has shifted focus to a new antibody test as the country's confirmed COVID-19 cases and deaths continue to roar. This test will help illuminate the extent to which COVID-19 has spread undetected in the country, and provide insights into which communities and populations are most affected as well as when should social distancing restrictions be lifted, experts told Xinhua on Saturday.

US Vice President Mike Pence said Friday that the United States is expected to have antibody test "very soon" that will determine whether somebody has been exposed to the coronavirus.

"Very soon, we will have an antibody test," Pence told a White House daily briefing. "Americans will be able to take to determine whether they ever had the coronavirus."

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said antibody testing can show who has developed immunity to the coronavirus and can safely go back to work without getting reinfected.

"It's very important to appreciate and understand how much this virus is penetrating this society," he said.

A large number of antibody tests should be available in a matter of days or weeks, according to Fauci.

Antibodies are the body's way of remembering how it responded to an infection, so it can attack again if exposed to the same pathogen.

The antibody test can determine if someone was previously infected and recovered, which is different from the molecular test showing whether that person was infected with the virus at the time the test was taken.

"The antibody test will be useful for those who had symptoms that seemed like COVID-19 but were, for one reason or another, not tested when they were sick. By the time they recover, the virus will no longer be detectable in the nose but antibodies will be present," Robert Schooley, a professor of medicine at the Division of Infectious Diseases and Global Public Health at the University of California, San Diego, told Xinhua.

Those with antibodies will likely not be vulnerable to reinfection with currently circulating strains of the virus, Schooley said. "This could also be very useful information for health care workers."

Antibody tests can also identify people who had COVID-19 but did not have any symptom, a group that may be much larger than expected.

"Antibody tests will help officials and researchers learn how often people are infected without symptoms. This will help us understand the epidemiology and the risk from 'under the radar' spread of the virus in the community," Schooley told Xinhua.

Widespread testing can determine how many people in the country carry the antibodies, which has an impact on whether and when to lift social distancing restrictions and impose other related measures.

Stanley Perlman, a professor of microbiology and immunology at the University of Iowa, told Xinhua that an antibody test, if reliable, will also inform us about who would be protected from infection in a second or third wave.

Immunity to viruses can last from months to a lifetime. Some experts expect that contracting the coronavirus once would likely give someone solid protection for a year. However, they warned a newly emerged virus is difficult to make predictions.

On Friday, a new study has begun recruiting at the US National Institutes of Health (NIH) to determine how many adults in the United States without a confirmed history of COVID-19 infection have antibodies to the virus.

Researchers will collect and analyze blood samples from as many as 10,000 volunteers to provide critical data for epidemiological models, said the NIH.

"These crucial data will help us measure the impact of our public health efforts now and guide our COVID-19 response moving forward," Fauci said.