Researchers identify risk factors for reinfection with SARS-CoV-2

A team of scientists from Capital Medical University and Peking University in China recently explored the factors responsible for the reactivation of coronavirus 2 (SARS-CoV-2) infection in severe acute respiratory syndrome in people who have recently recovered from coronavirus disease 2019 (COVID-19[FEMININE)TheresultsshowthatpeoplewithalowernumberoflymphocytesorwithtwosymptomsorduringthefirstepisodofCOVID-19areathigherriskofrecurrentinfectionfromthepast[FEMININE)LesrésultatsrévèlentquelespersonnesavecunnombredelymphocytesinférieurouavecdeuxsymptômesoumoinsaucoursdupremierépisodedeCOVID-19courentunrisqueplusélevéd’infectionrécurrenteL’étudeaétépubliéerécemmentdansleJournal of Infection and Public Health.

Study: Reactivation of SARS-CoV-2 infection after recovery from COVID-19.  Image Credit: NIAID / Flickr


Coronavirus disease 2019 (COVID-19) caused by SARS-CoV-2 is associated with a wide range of symptoms, including dry cough, fever, shortness of breath, fatigue, diarrhea, and loss of smell and / or taste. Although a considerable proportion of patients with COVID-19 remain asymptomatic or mildly symptomatic, the disease can often be fatal in susceptible people, including older adults and those with co-morbidities.

Studies characterizing host immunity linked to COVID-19 have found that binding and neutralizing antibodies developed in response to natural SARS-CoV-2 infection or vaccination can provide protection up to six months after the onset of symptoms. Additionally, a growing body of evidence has suggested the possibility of recurrent infection within days of recovery from COVID-19.

In the current study, scientists estimated the frequency of recurrent SARS-CoV-2 infections in individuals recovered from COVID-19. They also sought to identify the factors responsible for reinfection and relapse of the disease.

Study design

The study involved a total of 109 patients who had been admitted to a hospital in China with confirmed COVID-19. Scientists mainly estimated the frequency of reactivation of the infection at least 14 days after recovery or discharge from hospital by evaluating the results of recurrent positive tests for SARS-CoV-2 in two consecutive respiratory samples taken at more than 24 hour intervals.

In addition, by comparing individuals recovered from COVID-19 with and without positive recurrent test results for SARS-CoV-2, scientists identified the factors responsible for the reactivation of the infection and the relapse of COVID-19.

Important observations

Study participants were followed for an average of 29 days after discharge from hospital. During the follow-up period, 29 of 109 participants had recurrent positive test results for SARS-CoV-2. The mean duration of follow-up after discharge was 44 days and 28 days for patients with and without reinfection, respectively.

To assess the clinical features associated with reinfection and disease relapse, the scientists divided the participants into three groups: patients without reinfection, patients with reinfection, and patients with a relapse of COVID-19 (symptomatic patients). . Their analysis found that out of 29 re-infected patients, 7 developed symptomatic COVID-19 and 22 remained asymptomatic.

On further analysis, they noticed that patients with reinfection were relatively younger than those without reinfection. Likewise, the re-infected patients had experienced two or fewer symptoms during the first episode of COVID-19. Other clinical features of patients re-infected during the initial COVID-19 episode were the presence of secondary infection; higher than normal white blood cell count; lower than normal lymphocyte count; and increased blood circulation rate.

By carrying out a series of statistical analyzes, the scientists observed that a lymphocyte count of less than 1500 / µL and two or fewer symptoms during the initial episode of COVID-19 were the two independent predictors of re-infection with the virus. SARS-CoV-2 in COVID-19 individuals recovered. Regarding disease relapse, they observed that re-infected patients who developed symptoms (disease relapse) were significantly more likely to have had two or fewer symptoms during the initial episode of COVID- 19.

In patients with relapsed COVID-19, the mean SARS-CoV-2 seroconversion period has been estimated to be 17 days. In addition, the average time between hospital discharge and symptom relapse has been estimated to be six days.

Importance of the study

The study finds that patients with COVID-19 with a lymphocyte count of less than 1500 / µL or with two or fewer symptoms are at a higher risk of developing reinfection with SARS-CoV-2. Thus, individuals recovered from COVID-19 with these risk factors should be closely monitored for possible disease reactivation.