Observational study: prospective longitudinal cohort (Green)
The SARS-CoV-2 pandemic poses the greatest global public health challenge in a century. Neutralising antibody is a correlate of protection and data on kinetics of virus neutralising antibody responses are needed. In this article, the authors tested 293 sera from an observational cohort of 195 reverse transcription polymerase chain reaction (RT-PCR)-confirmed SARS-CoV-2 patients collected from 0 to 209 days after onset of symptoms. Of 115 sera collected ≥61 days after onset of illness, tested using plaque reduction neutralisation (PRNT) assays, 99.1% remained seropositive for both 90% (PRNT90) and 50% (PRNT50) neutralisation endpoints. The authors estimate that it takes at least 372, 416 and 133 days for PRNT50 titres to drop to the detection limit of a titre of 1:10 for severe, mild and asymptomatic patients, respectively. At day 90 after onset of symptoms (or initial RT-PCR detection in asymptomatic infections), it took 69, 87 and 31 days for PRNT50 antibody titres to decrease by half (T1/2) in severe, mild and asymptomatic infections, respectively. Patients with severe disease had higher peak PRNT90 and PRNT50 antibody titres than patients with mild or asymptomatic infections. Age did not appear to compromise antibody responses, even after accounting for disease severity.
The authors concluded that SARS-CoV-2 infection elicits robust neutralising antibody titres in most individuals.