Longitudinal changes in IgG levels among COVID-19 recovered patients: A prospective cohort study

Ashraf Hassan Alzaabi, Luai A. Ahmed, Abdulla E. Rabooy, Ali Al Zaabi, Mohammed Alkaabi, Falah AlMahmoud, Mai Farouk Hamed, Khalid Omar Bashaeb, Abdul Rahim Bakhsh, Suha Adil, Nadeen Elmajed, Ahmed Nigm Abousalha, Ahmad Kanaan Uwaydah, Khulood Al Mazrouei

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9 Citations (Scopus)


Objectives To quantify SARS-CoV2 IgG antibody titers over time and assess the longevity of the immune response in a multi-ethnic population setting. Setting This prospective study was conducted in a tertiary hospital in Abu Dhabi city, UAE, among COVID-19 confirmed patients. The virus-specific IgG were measured quantitatively in serum samples from the patients during three visits over a period of 6 months. Serum IgG levels 15 AU/ml was used to define a positive response. Participants 113 patients were analyzed at first visit, with a mean (SD) age of participants of 45.9 (11.8) years 87.5% of the patients were men. 63 and 27 participants had data available for visits 2 and 3, respectively. Primary outcome Change in SARS-CoV2 IgG antibody titers over the visits. Results No mortality or re-infection were reported. 69% of the patients developed positive IgG response within the first month after the onset of symptoms. The levels of IgG showed a consistent increase during the first three months with a peak level during the third month. Increasing trend in the levels of IgG were observed in 82.5%, 55.6% and 70.4% of patients between visit 1 to visit 2, visit 2 to visit 3, and from visit 1 to visit 3, respectively. Furthermore, about 64.3% of the patients showed sustained increase in IgG response for more than 120 days. Conclusions Our study indicates a sustained and prolonged positive immune response in COVID-19 recovered patients. The consistent rise in antibody and positive levels of IgG titers within the first 5 months suggest that immunization is possible, and the chances of reinfection minimal.

Original languageEnglish
Article numbere0251159
JournalPLoS ONE
Issue number6 June 2021
Publication statusPublished - Jun 2021

ASJC Scopus subject areas

  • General


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