The kinetics and predictors of anti-SARS-CoV-2 antibodies up to 8 months after symptomatic COVID-19: A Czech cross-sectional study
Abstract
The presence of neutralizing SARS-CoV-2-specific antibodies indicates protection against (re)infection, however, the knowledge of their long-term kinetics is limited. This study analyzed the presence of COVID-19-induced antibodies in unvaccinated healthcare workers (HCWs) over the period of 1-8 months post symptom onset (SO) and explored the determinants of persisting immunoglobulin (Ig) seropositivity.
Six hundred sixty-two HCWs were interviewed for anamnestic data and tested for IgG targeting the spike protein (S1 and S2) and IgM targeting the receptor-binding domain. A Cox regression model was used to explore potential predictors of seropositivity with respect to the time lapse between SO and serology testing. 82.9% and 44.7% of HCWs demonstrated IgG and IgM seropositivity, respectively, with a mean interval of 83 days between SARS-CoV-2 detection and serology testing.
On average, HCWs reported seven symptoms in the acute phase lasting 20 days. IgG seropositivity rates among HCWs decreased gradually to 80%, 50%, and 35% at 3, 6, and 8 months after SO, while IgM seropositivity fell rapidly to 60%, 15%, and 0% over the same time intervals.
The number of symptoms was the only predictor of persisting IgG seropositivity (odds ratio [OR] 1.096, 95% confidence interval [CI] 1.003-1.199, p = 0.043) and symptom duration a predictor of IgM seropositivity (OR 1.011, 95% CI 1.004-1.017, p = 0.002). Infection-induced anti-SARS-CoV-2 IgG rates drop to a third in seropositive participants over the course of 8 months.
Symptom count and duration in the acute phase of COVID-19 are both relevant to the subsequent kinetics of antibody responses.