• Alpaslan Turkkan, Imran Saglik, Cansu Turan, Ahmet Sahin, Halis Akalin, Beyza Ener, Ates Kara, Solmaz Celebi, Emre Sahin, and Mustafa Hacimustafaoglu.
• Department of Public Health, Bursa Uludag University Medical Faculty, Bursa, Turkey.
• Ir J Med Sci. 2022 Dec 1; 191 (6): 280328112803-2811.

BackgroundThe continual course of the pandemic points to the importance of studies on the rate and durability of protective immunity after infection or vaccination.AimsIn this study, we aimed to monitor anti-nucleocapsid (N) and anti-spike (S) antibodies against SARS-CoV-2 nearly 9 months duration after infection.MethodsAnti-nucleocapsid (N) (at 11-15-20-29-38 weeks) and anti-spike antibodies (at 11 and 38 weeks) against SARS-CoV-2 were monitored during 38 weeks after the initial symptoms of COVID-19.ResultsOf 37 cases between 18 and 57 years old, 54% were women. The findings showed that anti-N antibodies decreased significantly after the 15th week (between 15 and 20 weeks, p = 0.016; 20-29 weeks, p = 0.0009; and 29-38 weeks, p = 0.049). At the 38th week, mean antibody levels decreased 35% compared to the 11th week, and 8% of the cases turned negative results. Anti-N antibody average level was 56.48 on the 11th week (the cut-off index threshold ≥ 1). It was estimated statistically that it would decrease to an average of 20.48 in weeks 53-62. In females, average antibody levels of all measurements were lower than males (p > 0.05). Anti-S antibody levels 14% increased at 38th week compared to 11th week (quantitative positivity threshold ≥ 0.8 U/ml), and no cases were negative at 38th week.ConclusionsPatients had ≥ 90% positivity after at least 9 months of symptoms, both anti-N and anti-S antibodies. In all samples, both anti-N and anti-S antibody levels were lower in females. The findings suggest that the quantitative values of anti-S antibodies remained high for at least 9 months and could provide protection.© 2021. The Author(s), under exclusive licence to Royal Academy of Medicine in Ireland.

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