Viral RNA level, serum antibody responses, and transmission risk in discharged COVID-19 patients with recurrent positive SARS-CoV-2 RNA test results: a population-based observational cohort study

  1. Chao Yang
  2. Min Jiang
  3. Xiaohui Wang
  4. Xiujuan Tang
  5. Shisong Fang
  6. Hao Li
  7. Le Zuo
  8. Yixiang Jiang
  9. Yifan Zhong
  10. Qiongcheng Chen
  11. Chenli Zheng
  12. Lei Wang
  13. Shuang Wu
  14. Weihua Wu
  15. Hui Liu
  16. Jing Yuan
  17. Xuejiao Liao
  18. Zhen Zhang
  19. Yiman Lin
  20. Yijie Geng
  21. Huan Zhang
  22. Huanying Zheng
  23. Min Wan
  24. Linying Lu
  25. Xiaohu Ren
  26. Yujun Cui
  27. Xuan Zou
  28. Tiejian Feng
  29. Junjie Xia
  30. Ruifu Yang
  31. Yingxia Liu
  32. Shujiang Mei
  33. Baisheng Li
  34. Zhengrong Yang
  35. Qinghua Hu
2 evaluations Published on
Read the full article Related papers
This article on Sciety

Abstract

Summary

Background

Managing discharged COVID-19 (DC) patients with recurrent positive (RP) SARS-CoV-2 RNA test results is challenging. We aimed to comprehensively characterize the viral RNA level and serum antibody responses in RP-DC patients and evaluate their viral transmission risk.

Methods

A population-based observational cohort study was performed on 479 DC patients discharged from February 1 to May 5, 2020 in Shenzhen, China. We conducted RT-qPCR, antibody assays, neutralisation assays, virus isolation, whole genome sequencing (WGS), and epidemiological investigation of close contacts.

Findings

Of 479 DC patients, the 93 (19%) RP individuals, including 36 with multiple RP results, were characterised by young age (median age: 34 years, 95% confidence interval [CI]: 29–38 years). The median discharge-to-RP length was 8 days (95% CI: 7–14 days; maximum: 90 days). After readmission, RP-DC patients exhibited mild (28%) or absent (72%) symptoms, with no disease progression. The viral RNA level in RP-DC patients ranged from 1·9–5·7 log 10 copies/mL (median: 3·2, 95% CI: 3·1–3·5). At RP detection, the IgM, IgG, IgA, total antibody, and neutralising antibody (NAb) seropositivity rates in RP-DC patients were 38% (18/48), 98% (47/48), 63% (30/48), 100% (48/48), and 91% (39/43), respectively. Regarding antibody levels, there was no significant difference between RP-DC and non-RP-DC patients. The antibody level remained constant in RP-DC patients pre- and post-RP detection. Virus isolation of nine representative specimens returned negative results. WGS of six specimens yielded only genomic fragments. No clinical symptoms were exhibited by 96 close contacts of 23 RP-DC patients; their viral RNA (96/96) and antibody (20/20) test results were negative. After full recovery, 60% of patients (n=162, 78 no longer RP RP-DC and 84 non-RP-DC) had NAb titres of ≥1:32.

Interpretation

RP may occur in DC patients following intermittent and non-stable excretion of low viral RNA levels. RP-DC patients pose a low risk of transmitting SARS-CoV-2. An NAb titre of ≥ 1:32 may provide a reference indicator for evaluating humoral responses in COVID-19 vaccine clinical trials.

Funding

Sanming Project of Medicine in Shenzhen, China National Science and Technology Major Projects Foundation, Special Foundation of Science and Technology Innovation Strategy of Guangdong Province of China, and Shenzhen Committee of Scientific and Technical Innovation grants.

Related articles

Related articles are currently not available for this article.