Dynamics of neutralizing antibody responses to SARS-CoV-2 in patients with COVID-19: an observational study

Our understanding of the protective immunity,particularly the long-term dynamics of neutralizing antibody(NAbs)response to SARS-CoV-2,is currently limited.We enrolled a cohort of 545 COVID-19 patients from Hubei,China,who were followed up up to 7 months,and determined the dynamics of NAbs to SARS-CoV-2 by using a surrogate virus neutralization test(sVNT).In our validation study,sVNT IC50 titers and the neutralization rate measured at a single dilution(1:20)were well correlated with FRNT titers(r=0.85 and 0.84,respectively).The median time to seroconversion of NAbs was 5.5 days post onset of symptoms.The rate of positive sVNT was 52% in the first week,reached 100% in the third week,and remained above 97% till 6 months post onset.Quantitatively,NAbs peaked in the fourth week and only a quarter of patients had an estimated peak titer of>1000.NAbs declined with a half-time of 61 days(95%CI:49-80 days)within the first two months,and the decay deaccelerated to a half-time of 104 days(95%CI:86-130 days)afterward.The peak levels of NAbs were positively associated with severity of COVID-19 and age,while negatively associated with serum albumin levels.The observation that the low-moderate peak neutralizing activity and fast decay of NAbs in most naturally infected individuals called for caution in evaluating the feasibility of antibody-based therapy and vaccine durability.NAbs response positively correlated with disease severity,warning for the possibility of repeat infection in patients with mild COVID-19.