TITLE:
Long-Term Assessment of the Persistence of Anti-SARS-CoV-2 Antibodies in Vaccinated Healthcare Workers in the Republic of Congo
AUTHORS:
Jethro Massala Peya, Gilbert Ndziessi, Léadisaelle Hosanna Lenguiya, Jys Ryschel Ngoyomi-Alist, Joseph Axel Ngatse, Ange Clauvel Niama, GÉrard Eloko Eya Matangelo, Félix Koukouikila-Koussounda, Roch Fabien Niama
KEYWORDS:
COVID-19, Vaccination, Anti-SARS-CoV-2 Antibodies, Immune Persistence, Healthcare Workers
JOURNAL NAME:
Advances in Infectious Diseases,
Vol.15 No.3,
September
24,
2025
ABSTRACT: Introduction: Vaccination is a key strategy in the fight against the COVID-19 pandemic. The objective of this study is to evaluate the duration of vaccine protection through the persistence of anti-SARS-CoV-2 antibodies for up to 49 months in vaccinated healthcare workers. Methods: A cross-sectional study was conducted in healthcare facilities in Brazzaville. Serum samples were collected from healthcare workers and analyzed in the laboratory to measure the concentration of anti-S, anti-RBD, and anti-N antibodies using the MagPlex microsphere multiplex immunoassay method. The data were analyzed using R software, version 4.5.1. Results: The study included a total of 141 vaccinated healthcare workers, of whom 75.7% were female. The median age was 42.3 years (Q1 = 32 years, Q3=50 years), with a predominance of nurses (50.7%). The mean time since the last vaccine dose was 3.57 ± 0.43 years. The mean antibody concentrations were 13,353 IU/mL for anti-S (min = 14; max = 38,660), 33,224 IU/mL for anti-RBD (min = 1,026; max = 44,471), and 21,706 IU/mL for anti-N2 (min = 402; max = 42,839). The seroprevalence of anti-S antibodies (S+) was 83.0%. No significant differences were observed based on vaccine type, booster dose administration, or time elapsed since vaccination. Conclusion: This study highlights a high persistence of anti-SARS-CoV-2 antibodies up to 49 months after vaccination among healthcare workers in Brazzaville. None of the factors studied—vaccine type, booster dose, or time since vaccination—significantly influenced this seroprevalence. These findings suggest a potentially long-lasting post-vaccination immunity and underscore the importance of longitudinal monitoring to better understand the durability of immune protection over time.