COVID-19 Reinfection Risk Questioned After Low Levels Of Antibodies Found In Recovered Patients

Chinese scientists are hoping to find out whether recovered coronavirus patients have a higher risk of reinfection, after finding low levels of antibodies in people discharged from hospital in a small, preliminary study.

Researchers at Fudan University in Shanghai analysed blood sampled from 175 patients who had been released from the Shanghai Public Health Clinical Center. The results showed nearly a third had low levels of antibodies and in some patients, they could not be detected at all, the South China Morning Post reports.

An antibody is a Y-shaped protein secreted by certain types of white blood cells that have the ability to identify and neutralize pathogens such as viruses and bacteria.

The study, published in Medrxiv, has not been peer-reviewed. This means it is yet to be reviewed by a panel of experts who can judge the merit of the findings before it is published in a scientific journal. However, it is the first systematic research into antibody levels in patients who had recovered from COVID-19. The team say further research should be carried out into whether patients are at high risk of reinfection.

All of the patients had recently recovered from mild symptoms of the disease and most of those with low antibody levels were young. The researchers did not include patients who had been admitted to intensive care units because many of them already had antibodies from donated blood plasma—a treatment where serum from the blood of recovered patients is given to people with the virus to provide them with COVID-19 antibodies.

The researchers found that the antibody level in around a third of the patients may be too low to provide protection. "About 30 percent of patients failed to develop high titers [concentrations] of neutralizing antibodies after COVID-19 infection. However, the disease duration of these patients compared to others was similar," the researchers said.

Patients experiencing symptoms including a fever and a cough may have recovered from the virus using other areas of the immune system, such as T-cells of cytokines, but how this happened is unknown. The researchers also say the study also has implications for development of a vaccine. If the real virus could not induce an antibody response, the weakened version used in a vaccine may not work for some patients too.

Scientists across the globe are scrambling to find treatments for COVID-19. Along with plasma therapy, existing drugs are also being investigated for their potential benefits. These include the anti-malarial drug hydroxychloroquine and the the antiviral drug Favipiravir.

More recently, Australian researchers announced that a drug commonly used to treat parasite infections can also kill coronavirus in a laboratory setting in under 48 hours. The team, from Monash University in Melbourne, found that the antiparasitic drug Ivermectin can inhibit replication of SARS-CoV-2, the virus the causes COVID-19, according to a study published Friday in the journal Antiviral Research.

"Ivermectin is very widely used and seen as a safe drug. We need to figure out now whether the dosage you can use it at in humans will be effective—that's the next step," the study's leader Kylie Wagstaff said in a statement.

"We found that even a single dose could essentially remove all viral RNA by 48 hours and that even at 24 hours there was a really significant reduction in it."

Centers for Disease Control and Prevention Advice on Using Face Coverings to Slow Spread of COVID-19

  • CDC recommends wearing a cloth face covering in public where social distancing measures are difficult to maintain.
  • A simple cloth face covering can help slow the spread of the virus by those infected and by those who do not exhibit symptoms.
  • Cloth face coverings can be fashioned from household items. Guides are offered by the CDC.
  • Cloth face coverings should be washed regularly. A washing machine will suffice.
  • Practice safe removal of face coverings by not touching eyes, nose, and mouth, and wash hands immediately after removing the covering.

World Health Organization advice for avoiding spread of coronavirus disease (COVID-19)

Hygiene advice

  • Clean hands frequently with soap and water, or alcohol-based hand rub.
  • Wash hands after coughing or sneezing; when caring for the sick; before, during and after food preparation; before eating; after using the toilet; when hands are visibly dirty; and after handling animals or waste.
  • Maintain at least 1 meter (3 feet) distance from anyone who is coughing or sneezing.
  • Avoid touching your hands, nose and mouth. Do not spit in public.
  • Cover your mouth and nose with a tissue or bent elbow when coughing or sneezing. Discard the tissue immediately and clean your hands.

Medical advice

  • Avoid close contact with others if you have any symptoms.
  • Stay at home if you feel unwell, even with mild symptoms such as headache and runny nose, to avoid potential spread of the disease to medical facilities and other people.
  • If you develop serious symptoms (fever, cough, difficulty breathing) seek medical care early and contact local health authorities in advance.
  • Note any recent contact with others and travel details to provide to authorities who can trace and prevent spread of the disease.
  • Stay up to date on COVID-19 developments issued by health authorities and follow their guidance.

Mask and glove usage

  • Healthy individuals only need to wear a mask if taking care of a sick person.
  • Wear a mask if you are coughing or sneezing.
  • Masks are effective when used in combination with frequent hand cleaning.
  • Do not touch the mask while wearing it. Clean hands if you touch the mask.
  • Learn how to properly put on, remove and dispose of masks. Clean hands after disposing of the mask.
  • Do not reuse single-use masks.
  • Regularly washing bare hands is more effective against catching COVID-19 than wearing rubber gloves.
  • The COVID-19 virus can still be picked up on rubber gloves and transmitted by touching your face.
Shanghai Public Clinical Center China
A nurse walks inside a quarantine room at the Shanghai Public Clinical Center NOEL CELIS/POOL/AFP via Getty Images