[Monitoring of anti-SARS-CoV-2 IgG antibody immune responses in two cohorts of Hungarian healthcare workers following infection or immunization].
Gervain J., Szabóné Bartha K., Bakiné Hodovánszky E., Kadlecsik L., Herczeg R., Gyenesei A., Simon J.
Introduction: The length, level and variation of immune responses to infection with SARS-CoV-2 or following anti-SARS-CoV-2 vaccination remains unclear, optimal (re)vaccination protocols remain debated. Objective: We investigated the magnitude of humoral immune responses, their over-time changes, the frequency of (re)infections and the association with demographic and clinical parameters in Hungarian healthcare workers. Methods: We conducted a prospective, longitudinal study in two groups of healthcare workers of a public, county-level teaching hospital. Cohort 1: The anti-nucleocapsid IgG levels of 42 workers (female: 100%) were followed up over 8 months after SARS-CoV-2 infection (June 2020–February 2021). The change in humoral immune response and its associations with age, existing chronic conditions, blood type and severity of symptoms were investigated. Cohort 2: The anti-spike-RBD protein IgG levels of 49 workers (female: 73%) with no prior COVID–19 infection were monitored over 8 months (December 2020–August 2021) following immunisation with two doses of mRNA vaccine (Pfizer–BioNTech). Analyses included median analysis, linear regression, ANCOVA, Kruskal–Wallis and Skilling–Mack tests. Results: Cohort 1: IgG levels were on average the highest among those in illness severity category 4, the median time of IgG level reduction below the positive test cut-off was 6 months. Cohort 2: The IgG levels increased 25-fold between the first and second immunisations, but decreased to 6% of the peak level after 210 days. They showed an overall negative association with older age and male sex. The suspected levels of (re)infections were 17% and 14% within the infected and the immunised cohorts, respectively, all symptomless. Those affected all worked on high-risk wards. Conclusion: Both the infected and the immunised cohorts showed significantly declining IgG protections beyond 6 months. The average observed rate of (re)infections was 15%, all asymptomatic. Our findings are confirmative of the effectiveness of vaccination to prevent illness, the importance of booster vaccination due to declining humoral immune protection beyond 6 months, and the potential value of anti-SARS-CoV-2 IgG monitoring. Orv Hetil. 2022; 163(12): 455–462.