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. 2023 Mar 28;11(4):746.
doi: 10.3390/vaccines11040746.

The Effect of the Immunization Schedule and Antibody Levels (Anti-S) on the Risk of SARS-CoV-2 Infection in a Large Cohort of Healthcare Workers in Northern Italy

Emanuele Sansone  1 , Giulia Collatuzzo  2 , Stefano Renzetti  1 , Giorgia Ditano  2 , Carlo Bonfanti  3 , Emma Sala  4 , Luigina Terlenghi  3 , Alberto Matteelli  5 , Mahsa Abedini  2 , Shuffield Seyram Asafo  2 , Paolo Boffetta  2   6 , Giuseppe De Palma  1   4
Affiliations

The Effect of the Immunization Schedule and Antibody Levels (Anti-S) on the Risk of SARS-CoV-2 Infection in a Large Cohort of Healthcare Workers in Northern Italy

Emanuele Sansone et al. Vaccines (Basel). .

Abstract

Given their occupational risk profile, HCWs were the first to receive anti-SARS-CoV-2 vaccination. However, breakthrough infections remained common, mainly sustained by new SARS-CoV-2 variants of concern (VOCs) that rapidly spread one after another in Italy. Evidence suggests that the measured level of anti-SARS-CoV-2 antibodies does not clearly predict the level of protection conferred by either natural infection or vaccine-induced immunization, highlighting the need for further study on the diversity in susceptibility to SARS-CoV-2 infection. The present study aimed to characterize different risk profiles for SARS-CoV-2 infection in HCWs who had recently received the booster dose, and who were classified according to their immunization profile. The very small number of workers infected during the 8 months following the primary-cycle administration represents proof of the vaccine's effectiveness against non-omicron strains. The comparison among different immunization profiles showed that hybrid immunization (vaccine plus natural infection) elicits higher antibody levels. However, hybrid immunization does not always provide better protection against reinfection, thus suggesting that the immunization profile plays a major role as a virus-host interaction modifier. Despite the high resistance to the reinfection, the peri-booster infection had a not-neglectable infection rate (5.6%), this further reinforcing the importance of preventive measures.

Keywords: COVID-19 vaccines; HCWs; SARS-CoV-2; hybrid immunization; immunization profiles; serological response.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Trends of the anti-SARS-CoV-2-S levels (U/mL) over time in the whole sample stratified by the timing of the occurrence of previous SARS-CoV-2 infection. Curves were obtained from the predictions of the bootstrapped piecewise linear mixed model adjusted by age and gender. The day of the booster injection was set as the reference for time. The gap between the two periods (before and after the booster) was due to the absence of an anti-S serological assay performed during the interval between T3 and T4, when the booster dose was administered. Due to the infections occurred in such interval the no previous infection group was split in two, originating the peri-booster infection group, which curve can be only seen on the right part of the figure.
Figure 2
Figure 2
Kaplan–Meier curves measuring time without infection obtained according to the considered immunization profiles. The booster injection date was considered a reference for the time axis.
See this image and copyright information in PMC

References

    1. Scortichini M., Schneider Dos Santos R., De’ Donato F., De Sario M., Michelozzi P., Davoli M., Masselot P., Sera F., Gasparrini A. Excess mortality during the COVID-19 outbreak in Italy: A two-stage interrupted time-series analysis. Int. J. Epidemiol. 2021;49:1909–1917. doi: 10.1093/ije/dyaa169. - DOI - PMC - PubMed
    1. Data Repository for COVID-19 Infection by the Center for Systems Science and Engineering (CSSE) [(accessed on 22 November 2022)]. Available online: https://github.com/CSSEGISandData/COVID-19.
    1. Gómez-Ochoa S.A., Franco O.H., Rojas L.Z., Raguindin P.F., Roa-Díaz Z.M., Wyssmann B.M., Guevara S.L.R., Echeverría L.E., Glisic M., Muka T. COVID-19 in Health-Care Workers: A Living Systematic Review and Meta-Analysis of Prevalence, Risk Factors, Clinical Characteristics, and Outcomes. Am. J. Epidemiol. 2021;190:161–175. doi: 10.1093/aje/kwaa191. Erratum in Am. J. Epidemiol. 2021, 190, 187. - DOI - PMC - PubMed
    1. Sansone E., Sala E., Albini E., Tiraboschi M., Cipriani L., De Palma G. Effectiveness of a digital data gathering system to manage the first pandemic wave among healthcare workers in a main European coronavirus disease 2019 (COVID-19) tertiary-care hospital. Antimicrob. Steward. Healthc. Epidemiol. 2022;2:E66. doi: 10.1017/ash.2022.48. - DOI - PMC - PubMed
    1. Sansone E., Bonfanti C., Sala E., Renzetti S., Terlenghi L., Matteelli A., Tiraboschi M.M., Pedrazzi T., Lombardo M., Rossi C., et al. Immune Responses to SARS-CoV-2 Infection and Vaccine in a Big Italian COVID-19 Hospital: An 18-Month Follow-Up. Vaccines. 2023;11:8. doi: 10.3390/vaccines11010008. - DOI - PMC - PubMed

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