Abstract
Objectives: To describe a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) B.1.617.2 (Delta) variant outbreak among residents (n = 69) and health workers (n = 69) of a small nursing home in northeastern Italy, with full vaccination coverage of 91% and 82%, respectively. Evaluation of the anti-Spike IgG titres 28 weeks after the mRNA vaccine booster dose against SARS-CoV-2 infection and severe coronavirus disease 2019 (COVID-19).
Materials and methods: Sera were collected within 48 hours from the index case; anti-Spike IgG was determined (expressed as WHO binding antibody units (BAU)/mL) through a commercial quantitative assay; SARS-CoV-2 was diagnosed using RT-PCR, and full-genome sequencing was performed for lineage characterization. Residents were grouped according to anti-Spike IgG titres (≤50, 51-1000 and > 1000 BAU/mL) and the resulting protection against infection and severe disease was measured.
Results: None of the health workers and 14 of the 59 (24%) residents fully vaccinated and without a previous SARS-CoV-2 infection showed anti-Spike IgG ≤50 BAU/mL (one-sided Fisher exact test, p 0.011). Among these residents, a level of anti-Spike IgG ≤50 BAU/mL resulted in a higher risk of SARS-CoV-2 infection (relative risk 1.55, 95% CI 1.17-2.05) and severe COVID-19 (relative risk 5.33, 95% CI 1.83-15.57).
Conclusion: Low levels of SARS-CoV-2 neutralizing anti-Spike IgG in serum 28 weeks after the administration of the second dose parallel the waning of vaccine protection.
Keywords: Anti-Spike IgG; B.1.617.2 SARS-CoV-2 variant; Immunity; Nursing home residents; Outbreak; Vaccine effectiveness.
【저자키워드】 Immunity, anti-Spike IgG, outbreak, vaccine effectiveness, nursing home residents, B.1.617.2 SARS-CoV-2 variant, 【초록키워드】 COVID-19, coronavirus disease, SARS-CoV-2, IgG, Coronavirus disease 2019, Vaccine, coronavirus, vaccination, health workers, severe COVID-19, mRNA vaccine, SARS-COV-2 infection, nursing home, Sequencing, variant, Infection, Delta, B.1.617.2, risk, Italy, severe acute respiratory syndrome Coronavirus, RT-PCR, Relative risk, resident, serum, Coverage, anti-Spike IgG, sera, Lineage, Effectiveness, WHO, Neutralizing, respiratory, Quantitative, booster dose, Anti-spike, administration, health worker, severe disease, index case, 48 hours, Antibody Units, acute respiratory syndrome, higher risk, 95% CI, acute respiratory syndrome coronavirus, acute respiratory syndrome coronavirus 2, severe coronavirus disease, second dose, titre, material, Fisher exact test, was measured, resulting, collected, diagnosed, was performed, was determined, expressed, 48 hour, binding antibody unit, 【제목키워드】 SARS-CoV-2, variant, B.1.617.2, mRNA, Evidence, dose, waning immunity,