"Severe COVID-19 Symptoms Make Reinfection Less Likely" ... Domestic Research Findings

"More Severe Symptoms Lead to Longer-lasting Neutralizing Antibodies"

On the 22nd of last month, when 99,573 new COVID-19 cases were reported, citizens visiting the temporary screening clinic set up at Seoul Station Plaza were waiting to get tested. Photo by Asia Economy

[Asia Economy Reporter Na Ye-eun] A study has found that the more severe the symptoms experienced after COVID-19 infection, the longer the 'neutralizing antibodies' that neutralize variant viruses and prevent reinfection persist.

On the 1st, according to the medical community, a research team led by Professors Oh Myung-don, Park Wan-beom, and Choi Pyeong-gyun from the Department of Infectious Diseases at Seoul National University Hospital published in the Journal of Korean Medical Science (JKMS) the results of evaluating the neutralization capacity up to 12 months after infection in 16 patients confirmed during the early domestic COVID-19 outbreak.

The research team conducted a 12-month follow-up observation of 16 early COVID-19 patients admitted to the isolation ward of Seoul National University Hospital from February to June 2020. Among them, 8 were severe patients who required oxygen therapy due to pneumonia caused by COVID-19, 4 had mild symptoms, and 4 were asymptomatic.

None of the 16 patients received COVID-19 vaccination during the study period.

The team measured the neutralizing antibody titers (the amount of antibodies providing preventive effects) using the focus reduction neutralization test (FRNT). FRNT is a test that stains virus-infected cells and observes how much the size of the clustered areas (focus) decreases over time. If neutralizing antibodies are present in the patient's body, the stained cells decrease over time after infection, and this reduction is used to calculate the neutralizing antibody titers.

The study results showed that neutralizing antibodies against the Delta variant were detected in severe COVID-19 patients, but not in asymptomatic patients.

The research team stated, "The duration of neutralizing antibodies against variant viruses in COVID-19 patients varies according to symptom severity, and the neutralizing antibody response lasts longer in severe patients," adding, "Asymptomatic confirmed cases should not delay vaccination even after recovering from COVID-19."

However, the team noted that the possibility of reinfection cannot be completely ruled out even in those who experienced severe symptoms. This is because it was uncommon for neutralizing antibodies against variant viruses to be maintained up to 12 months after infection, even in severe patients.