{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,19]],"date-time":"2026-10-19T21:05:00Z","timestamp":1792443900894,"version":"4.5.0"},"reference-count":66,"publisher":"MDPI AG","issue":"5","license":[{"start":{"date-parts":[[2026,4,24]],"date-time":"2026-04-24T00:00:00Z","timestamp":1776988800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100020275","name":"Vilnius University","doi-asserted-by":"crossref","id":[{"id":"10.13039\/501100020275","id-type":"DOI","asserted-by":"crossref"}]},{"id":[{"id":"https:\/\/ror.org\/03nadee84","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Medicina"],"abstract":"<jats:p>Background and Objectives: Healthcare workers are at heightened risk of SARS-CoV-2 infection. Understanding the duration and protective value of vaccine-induced immunity is critical to inform booster strategies. This study investigates longitudinal dynamics of anti-SARS-CoV-2 receptor-binding domain IgG (anti-RBD IgG) antibodies and their association with infection risk among vaccinated healthcare workers. Materials and Methods: A prospective cohort study was conducted at Vilnius University Hospital Santaros Klinikos, Lithuania. A total of 1778 healthcare workers who completed a primary COVID-19 vaccination series were followed. Blood samples were collected every three months to measure anti-RBD IgG levels. Participants also received up to three booster doses. COVID-19 was identified by PCR, antigen tests, or positive anti-nucleocapsid IgG. For serologically detected cases, infection timing was assigned to the interval between study visits. Antibody dynamics were analyzed across vaccination stages, time, age groups, and circulating SARS-CoV-2 variants. Results: Anti-RBD IgG titers peaked in the first quarter after primary vaccination (mean 7904 AU\/mL), declined sharply by quarters 2\u20133, and rose substantially after booster doses. Following the first booster, titers increased to ~12,598 AU\/mL in quarter 1 and continued rising through quarter 3. The highest levels were observed after the second booster (24,456 AU\/mL in Q1), followed by gradual decline. A high-titer plateau persisted from quarters 6 to 9 (~21,000 AU\/mL), followed by decline in quarters 10\u201311 and partial rebound in Q12. Approximately 49.6% of participants experienced COVID-19 during follow-up. Antibody response patterns were similar across age groups, with only minor transient differences. Conclusions: COVID-19 booster doses significantly enhance and prolong humoral immunity in healthcare workers compared with the primary vaccination series. However, antibody waning over time emphasizes the need for timely boosters, particularly during periods of variant circulation. These findings support continued booster vaccination and monitoring of long-term immune protection, although anti-RBD IgG should be interpreted as a surrogate marker of humoral rather than overall immunity.<\/jats:p>","DOI":"10.3390\/medicina62050810","type":"journal-article","created":{"date-parts":[[2026,4,24]],"date-time":"2026-04-24T17:26:18Z","timestamp":1777051578000},"page":"810","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Dynamics and Protective Effectiveness of Serological Testing Among Healthcare Workers Vaccinated Against COVID-19"],"prefix":"10.3390","volume":"62","author":[{"given":"Vilija","family":"Gurk\u0161nien\u0117","sequence":"first","affiliation":[{"name":"Faculty of Medicine, Vilnius University, 03101 Vilnius, Lithuania"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Tadas","family":"Al\u010dauskas","sequence":"additional","affiliation":[{"name":"Faculty of Medicine, Vilnius University, 03101 Vilnius, Lithuania"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Dovil\u0117","family":"Karosien\u0117","sequence":"additional","affiliation":[{"name":"Vilnius University Hospital Santaros Clinics, 08410 Vilnius, Lithuania"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jurgita","family":"Urbonien\u0117","sequence":"additional","affiliation":[{"name":"Vilnius University Hospital Santaros Clinics, 08410 Vilnius, Lithuania"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0007-4307-9547","authenticated-orcid":false,"given":"Fausta","family":"Majauskait\u0117","sequence":"additional","affiliation":[{"name":"Faculty of Medicine, Vilnius University, 03101 Vilnius, Lithuania"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9671-4053","authenticated-orcid":false,"given":"Mindaugas","family":"Paulauskas","sequence":"additional","affiliation":[{"name":"Faculty of Medicine, Vilnius University, 03101 Vilnius, Lithuania"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Birut\u0117","family":"Zablockien\u0117","sequence":"additional","affiliation":[{"name":"Faculty of Medicine, Vilnius University, 03101 Vilnius, Lithuania"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0912-4125","authenticated-orcid":false,"given":"Dalius","family":"Vitkus","sequence":"additional","affiliation":[{"name":"Faculty of Medicine, Vilnius University, 03101 Vilnius, Lithuania"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6488-6312","authenticated-orcid":false,"given":"Ligita","family":"Jan\u010dorien\u0117","sequence":"additional","affiliation":[{"name":"Faculty of Medicine, Vilnius University, 03101 Vilnius, Lithuania"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,4,24]]},"reference":[{"key":"ref_1","unstructured":"WHO (2025, October 26). Coronavirus (COVID-19) Dashboard. Overview. Available online: https:\/\/data.who.int\/dashboards\/covid19\/cases?n=c."},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"CDC COVID-19 Response Team, Burrer, S.L., de Perio, M.A., Hughes, M.M., Kuhar, D.T., Luckhaupt, S.E., McDaniel, C.J., Porter, R.M., Silk, B., and Stuckey, M.J. (2020). Characteristics of Health Care Personnel with COVID-19\u2014United States, February 12\u2013April 9, 2020. MMWR Morb. Mortal. Wkly. Rep., 69, 477\u2013481.","DOI":"10.15585\/mmwr.mm6915e6"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"taaa094","DOI":"10.1093\/jtm\/taaa094","article-title":"Exposure to SARS-CoV-2 in a high transmission setting increases the risk of severe COVID-19 compared with exposure to a low transmission setting?","volume":"27","author":"Chen","year":"2020","journal-title":"J. Travel Med."},{"key":"ref_4","first-page":"00080","article-title":"The protective effect of SARS-CoV-2 antibodies in Scottish healthcare workers","volume":"7","author":"Gallant","year":"2021","journal-title":"ERJ Open Res."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"58","DOI":"10.1186\/s12985-021-01532-0","article-title":"COVID-19 infection among healthcare workers: A cross-sectional study in southwest Iran","volume":"18","author":"Sabetian","year":"2021","journal-title":"Virol. J."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"1089","DOI":"10.1136\/thoraxjnl-2020-215414","article-title":"SARS-CoV-2 seroprevalence and asymptomatic viral carriage in healthcare workers: A cross-sectional study","volume":"75","author":"Shields","year":"2020","journal-title":"Thorax"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"32","DOI":"10.1016\/j.ijid.2020.10.009","article-title":"Characteristics of healthcare workers infected with COVID-19: A cross-sectional observational study","volume":"102","author":"Khamis","year":"2021","journal-title":"Int. J. Infect. Dis."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"161","DOI":"10.1093\/aje\/kwaa191","article-title":"COVID-19 in Health-Care Workers: A Living Systematic Review and Meta-Analysis of Prevalence, Risk Factors, Clinical Characteristics, and Outcomes","volume":"190","author":"Franco","year":"2021","journal-title":"Am. J. Epidemiol."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"2439","DOI":"10.1056\/NEJMoa2027906","article-title":"Safety and Immunogenicity of Two RNA-Based COVID-19 Vaccine Candidates","volume":"383","author":"Walsh","year":"2020","journal-title":"N. Engl. J. Med."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"2603","DOI":"10.1056\/NEJMoa2034577","article-title":"Safety and Efficacy of the BNT162b2 mRNA COVID-19 Vaccine","volume":"383","author":"Polack","year":"2020","journal-title":"N. Engl. J. Med."},{"key":"ref_11","unstructured":"European Commission (2025, October 26). Statement by President von der Leyen on the Marketing Authorisation of the BioNTech\u2013Pfizer Vaccine against COVID-19; Statement, Brussels, Belgium. Available online: https:\/\/ec.europa.eu\/commission\/presscorner\/detail\/en\/STATEMENT_20_2510."},{"key":"ref_12","unstructured":"World Health Organization (2025, October 26). Coronavirus Disease (COVID-19): Vaccine Access and Allocation. Available online: https:\/\/www.who.int\/news-room\/q-a-detail\/coronavirus-disease-(covid-19)-vaccine-access-and-allocation."},{"key":"ref_13","unstructured":"Ministry of Health of the Republic of Lithuania (2025, October 26). \u012esakymas D\u0117l Skiepijimo Valstyb\u0117s Biud\u017eeto L\u0117\u0161omis \u012esigyjama COVID-19 Ligos (Koronaviruso Infekcijos) Vakcina Prioritetin\u0117s Gyventoj\u0173 Grup\u0117s Patvirtinimo, 23 December 2020, No. V-3006, Vilnius, Lithuania. Available online: https:\/\/e-seimas.lrs.lt\/portal\/legalAct\/lt\/TAD\/fd056f90469711ebb394e1efb98d3e67."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"1725","DOI":"10.1016\/S0140-6736(21)00790-X","article-title":"COVID-19 Vaccine Coverage in Health-Care Workers in England and Effectiveness of BNT162b2 mRNA Vaccine against Infection (SIREN): A Prospective, Multicentre, Cohort Study","volume":"397","author":"Hall","year":"2021","journal-title":"Lancet"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"2457","DOI":"10.1001\/jama.2021.7152","article-title":"Association Between Vaccination with BNT162b2 and Incidence of Symptomatic and Asymptomatic SARS-CoV-2 Infections among Health Care Workers","volume":"325","author":"Angel","year":"2021","journal-title":"JAMA"},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Bouton, T.C., Lodi, S., Turcinovic, J., Weber, S.E., Quinn, E., Korn, C., Steiner, J., Schechter-Perkins, E.M., Duffy, E., and Ragan, E.J. (2021). COVID-19 Vaccine Impact on Rates of SARS-CoV-2 Cases and Post-Vaccination Strain Sequences among Healthcare Workers at an Urban Academic Medical Center: A Prospective Cohort Study. medRxiv.","DOI":"10.1101\/2021.03.30.21254655"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"1474","DOI":"10.1056\/NEJMoa2109072","article-title":"COVID-19 Breakthrough Infections in Vaccinated Health Care Workers","volume":"385","author":"Bergwerk","year":"2021","journal-title":"N. Engl. J. Med."},{"key":"ref_18","unstructured":"Centers for Disease Control and Prevention (2025, October 26). Delta Variant: What We Know About the Science, Available online: https:\/\/stacks.cdc.gov\/view\/cdc\/108671."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"585","DOI":"10.1056\/NEJMoa2108891","article-title":"Effectiveness of COVID-19 Vaccines against the B.1.617.2 (Delta) Variant","volume":"385","author":"Andrews","year":"2021","journal-title":"N. Engl. J. Med."},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Anastassopoulou, C., Antoni, D., Manoussopoulos, Y., Stefanou, P., Argyropoulou, S., Vrioni, G., and Tsakris, A. (2022). Age and sex associations of SARS-CoV-2 antibody responses post BNT162b2 vaccination in healthcare workers: A mixed effects model across two vaccination periods. PLoS ONE, 17.","DOI":"10.1371\/journal.pone.0266958"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"650","DOI":"10.1016\/j.vaccine.2021.12.014","article-title":"Humoral response to the SARS-CoV-2 BNT162b2 mRNA vaccine: Real-world data from a large cohort of healthcare workers","volume":"40","author":"Reis","year":"2022","journal-title":"Vaccine"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"e4","DOI":"10.1016\/j.jinf.2021.06.024","article-title":"Three-month analysis of total humoral response to Pfizer BNT162b2 mRNA COVID-19 vaccination in healthcare workers","volume":"83","author":"Salvagno","year":"2021","journal-title":"J. Infect."},{"key":"ref_23","doi-asserted-by":"crossref","unstructured":"Bayart, J.L., Douxfils, J., Gillot, C., David, C., Mullier, F., Elsen, M., Eucher, C., Van Eeckhoudt, S., Roy, T., and Gerin, V. (2021). Waning of IgG, Total and Neutralizing Antibodies 6 Months Post-Vaccination with BNT162b2 in Healthcare Workers. Vaccines, 9.","DOI":"10.21203\/rs.3.rs-862966\/v1"},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"\u0110akovi\u0107 Rode, O., Boduli\u0107, K., Zember, S., Cetini\u0107 Balent, N., Novokmet, A., \u010culo, M., Ra\u0161i\u0107, \u017d., Mikuli\u0107, R., and Markoti\u0107, A. (2022). Decline of Anti-SARS-CoV-2 IgG Antibody Levels 6 Months after Complete BNT162b2 Vaccination in Healthcare Workers to Levels Observed Following the First Vaccine Dose. Vaccines, 10.","DOI":"10.3390\/vaccines10020153"},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Krintus, M., Piasecki, M., Lackowski, P., Buszko, K., Kubica, A., Kosobucka-Ozdoba, A., Michalski, P., Pietrzykowski, L., Stolarek, W., and Wojcik, A. (2022). Determinants of the Level of Anti-SARS-CoV-2 IgG ANTibodiEs after Vaccination (DANTE-SIRIO 7) Study in a Large Cohort of Healthcare Workers. Vaccines, 10.","DOI":"10.3390\/vaccines10122125"},{"key":"ref_26","first-page":"1","article-title":"Long-term serological SARS-CoV-2 IgG kinetics following mRNA COVID-19 vaccine: Real-world data from a large cohort of healthcare workers","volume":"122","author":"Reis","year":"2022","journal-title":"Int. J. Infect. Dis."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"1969","DOI":"10.1111\/jam.15699","article-title":"Assessment of humoral immune response to two mRNA SARS-CoV-2 vaccines (Moderna and Pfizer) in healthcare workers fully vaccinated with and without a history of previous infection","volume":"133","author":"Serrano","year":"2022","journal-title":"J. Appl. Microbiol."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"115638","DOI":"10.1016\/j.diagmicrobio.2022.115638","article-title":"IgG anti-spike antibody levels in healthcare workers with and without prior COVID-19 up to 3 months after BNT162b2 vaccination","volume":"102","author":"Weemaes","year":"2022","journal-title":"Diagn. Microbiol. Infect. Dis."},{"key":"ref_29","first-page":"e2022022","article-title":"Serological response after SARS-CoV2 vaccination in healthcare workers: A multicenter study","volume":"113","author":"Visci","year":"2022","journal-title":"Med. Lav."},{"key":"ref_30","unstructured":"(2024, September 26). IgG Antibodies Against SARS-CoV-2 Decay But Persist 4 Months After Vaccination in a Cohort of Healthcare Workers, Available online: https:\/\/pubmed.ncbi.nlm.nih.gov\/34755649\/."},{"key":"ref_31","doi-asserted-by":"crossref","unstructured":"Cangemi, R., Di Franco, M., Angeloni, A., Zicari, A., Cardinale, V., Visentini, M., Antonelli, G., Napoli, A., Anastasi, E., and Romiti, G.F. (2022). Serological Response and Relationship with Gender-Sensitive Variables among Healthcare Workers after SARS-CoV-2 Vaccination. J. Pers. Med., 12.","DOI":"10.3390\/jpm12060994"},{"key":"ref_32","doi-asserted-by":"crossref","unstructured":"Fern\u00e1ndez-Rivas, G., Barallat, J., Quirant-S\u00e1nchez, B., Gonz\u00e1lez, V., Dolad\u00e9, M., Martinez-Caceres, E., Pi\u00f1a, M., Matllo, J., Blanco, I., and Cardona, P.J. (2022). Follow up of the Humoral Response in Healthcare Workers after the Administration of Two Dose of the Anti SARS-CoV-2 Vaccines-Effectiveness in Delta Variant Breakthrough Infections. Viruses, 14.","DOI":"10.3390\/v14071385"},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"934","DOI":"10.1515\/cclm-2022-0170","article-title":"The role of neutralizing antibodies by sVNT after two doses of BNT162b2 mRNA vaccine in a cohort of Italian healthcare workers","volume":"60","author":"Infantino","year":"2022","journal-title":"Clin. Chem. Lab. Med."},{"key":"ref_34","doi-asserted-by":"crossref","unstructured":"Ramos, A., Cardoso, M.J., Ribeiro, L., and Guimar\u00e3es, J.T. (2022). Assessing SARS-CoV-2 Neutralizing Antibodies after BNT162b2 Vaccination and Their Correlation with SARS-CoV-2 IgG Anti-S1, Anti-RBD and Anti-S2 Serological Titers. Diagnostics, 12.","DOI":"10.3390\/diagnostics12010205"},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"e24175","DOI":"10.1002\/jcla.24175","article-title":"Time course of antibody concentrations against the spike protein of SARS-CoV-2 among healthy hospital workers up to 200 days after their first COVID-19 vaccination","volume":"36","author":"Mueller","year":"2022","journal-title":"J. Clin. Lab. Anal."},{"key":"ref_36","doi-asserted-by":"crossref","unstructured":"Gil-Manso, S., Alonso, R., Catal\u00e1n, P., S\u00e1nchez-Arcilla, I., Marzola, M., Correa-Rocha, R., Pion, M., Mu\u00f1oz, P., and Gregorio Mara\u00f1\u00f3n Microbiology-ID COVID-19 Study Group (2022). IgG anti-RBD levels during 8-month follow-up post-vaccination with BNT162b2 and mRNA-1273 vaccines in healthcare workers: A one-center study. Front. Cell. Infect. Microbiol., 12.","DOI":"10.3389\/fcimb.2022.1035155"},{"key":"ref_37","doi-asserted-by":"crossref","unstructured":"Golec, M., Fronczek, M., Zembala-John, J., Chrapiec, M., Konka, A., Wystyrk, K., Botor, H., Brzoza, Z., Kasperczyk, S., and Bu\u0142dak, R.J. (2022). Early and Longitudinal Humoral Response to the SARS-CoV-2 mRNA BNT162b2 Vaccine in Healthcare Workers: Significance of BMI, Adipose Tissue and Muscle Mass on Long-Lasting Post-Vaccinal Immunity. Viruses, 14.","DOI":"10.3390\/v14050868"},{"key":"ref_38","doi-asserted-by":"crossref","unstructured":"Wolszczak-Biedrzycka, B., Bie\u0144kowska, A., and Dorf, J. (2021). Assessment of Post-Vaccination Antibody Response Eight Months after the Administration of BNT1622b2 Vaccine to Healthcare Workers with Particular Emphasis on the Impact of Previous COVID-19 Infection. Vaccines, 9.","DOI":"10.3390\/vaccines9121508"},{"key":"ref_39","doi-asserted-by":"crossref","unstructured":"Inchingolo, A.D., Malcangi, G., Ceci, S., Patano, A., Corriero, A., Azzollini, D., Marinelli, G., Coloccia, G., Piras, F., and Barile, G. (2022). Antispike Immunoglobulin-G (IgG) Titer Response of SARS-CoV-2 mRNA-Vaccine (BNT162b2): A Monitoring Study on Healthcare Workers. Biomedicines, 10.","DOI":"10.3390\/biomedicines10102402"},{"key":"ref_40","doi-asserted-by":"crossref","unstructured":"Collatuzzo, G., De Palma, G., Violante, F.S., Porru, S., Larese Filon, F., Fabianova, E., Viol\u00e1n, C., Vimercati, L., Leustean, M., and Rodriguez-Suarez, M.M. (2023). Temporal trends of COVID-19 antibodies in vaccinated healthcare workers undergoing repeated serological sampling: An individual-level analysis within 13 months in the ORCHESTRA cohort. Front Immunol., 13.","DOI":"10.3389\/fimmu.2022.1079884"},{"key":"ref_41","doi-asserted-by":"crossref","unstructured":"Lorent, D., Nowak, R., Figlerowicz, M., Handschuh, L., and Zmora, P. (2024). Anti-SARS-CoV-2 Antibodies Level and COVID-19 Vaccine Boosters among Healthcare Workers with the Highest SARS-CoV-2 Infection Risk-Follow Up Study. Vaccines, 12.","DOI":"10.3390\/vaccines12050475"},{"key":"ref_42","first-page":"432","article-title":"COVID-19 Immunity in the Cohort of IRCCS San Raffaele Hospital Employees after BNT162b2 Vaccination: A Retrospective Observational Study","volume":"36","author":"Stocchi","year":"2024","journal-title":"Ann. Ig."},{"key":"ref_43","doi-asserted-by":"crossref","unstructured":"Chivu-Economescu, M., Vremera, T., Ruta, S.M., Grancea, C., Leustean, M., Chiriac, D., David, A., Matei, L., Diaconu, C.C., and Gatea, A. (2022). Assessment of the Humoral Immune Response Following COVID-19 Vaccination in Healthcare Workers: A One Year Longitudinal Study. Biomedicines, 10.","DOI":"10.3390\/biomedicines10071526"},{"key":"ref_44","unstructured":"(2024, September 26). Long Follow-Up of BNT162b2 mRNA Vaccine in Healthcare Workers (2020\u20132022): A Retrospective Longitudinal SARS-CoV-2 Serological Surveillance, Available online: https:\/\/pubmed.ncbi.nlm.nih.gov\/37724517\/."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"2200746","DOI":"10.2807\/1560-7917.ES.2023.28.15.2200746","article-title":"A third vaccine dose equalises the levels of effectiveness and immunogenicity of heterologous or homologous COVID-19 vaccine regimens, Lyon, France, December 2021 to March 2022","volume":"28","author":"Guibert","year":"2023","journal-title":"Eurosurveillance"},{"key":"ref_46","doi-asserted-by":"crossref","unstructured":"Leomanni, L., Collatuzzo, G., Sansone, E., Sala, E., De Palma, G., Porru, S., Spiteri, G., Monaco, M.G.L., Basso, D., and Pavanello, S. (2023). Determinants of Anti-S Immune Response at 12 Months after SARS-CoV-2 Vaccination in a Multicentric European Cohort of Healthcare Workers-ORCHESTRA Project. Vaccines, 11.","DOI":"10.3390\/vaccines11101527"},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"1110","DOI":"10.1515\/cclm-2022-0322","article-title":"A cohort analysis of SARS-CoV-2 anti-spike protein receptor binding domain (RBD) IgG levels and neutralizing antibodies in fully vaccinated healthcare workers","volume":"60","author":"Padoan","year":"2022","journal-title":"Clin. Chem. Lab. Med."},{"key":"ref_48","doi-asserted-by":"crossref","unstructured":"Pavlidis, G., Giannoulis, V., Pirounaki, M., Lampropoulos, I.C., Siafi, E., Nitsa, A., Pavlou, E., Xanthaki, A., Perlepe, G., and Fortis, S.P. (2023). Evaluation of Antibody Kinetics Following COVID-19 Vaccination in Greek SARS-CoV-2 Infected and Na\u00efve Healthcare Workers. J. Pers. Med., 13.","DOI":"10.3390\/jpm13060910"},{"key":"ref_49","doi-asserted-by":"crossref","unstructured":"Skorupa, M., Szczepanek, J., Goroncy, A., Jarkiewicz-Tretyn, J., Ptaszy\u0144ska, B., Rajewski, P., Koper, W., Pa\u0142gan, K., and Tretyn, K. (2022). The Dynamics of Changes in the Concentration of IgG against the S1 Subunit in Polish Healthcare Workers in the Period from 1 to 12 Months after Injection, Including Four COVID-19 Vaccines. Vaccines, 10.","DOI":"10.3390\/vaccines10040506"},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"5726","DOI":"10.1016\/j.vaccine.2022.08.045","article-title":"Antibody levels after BNT162b2 vaccine booster and SARS-CoV-2 Omicron infection","volume":"40","author":"Vietri","year":"2022","journal-title":"Vaccine"},{"key":"ref_51","doi-asserted-by":"crossref","unstructured":"Gerhards, C., Thiaucourt, M., Hetjens, M., Haselmann, V., Neumaier, M., and Kittel, M. (2023). Heterologous Vector-mRNA Based SARS-CoV-2 Vaccination Strategy Appears Superior to a Homologous Vector-Based Vaccination Scheme in German Healthcare Workers Regarding Humoral SARS-CoV-2 Response Indicating a High Boosting Effect by mRNA Vaccines. Vaccines, 11.","DOI":"10.3390\/vaccines11030701"},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"1948","DOI":"10.3390\/vaccines10111948","article-title":"Kinetics of Humoral Immunity against SARS-CoV-2 in Healthcare Workers after the Third Dose of BNT162b2 mRNA Vaccine","volume":"10","author":"Grassi","year":"2022","journal-title":"Vaccines"},{"key":"ref_53","doi-asserted-by":"crossref","unstructured":"Skrzat-Klapaczy\u0144ska, A., Kowalska, J.D., Paciorek, M., Pu\u0142a, J., Bie\u0144kowski, C., Krogulec, D., Stengiel, J., Pawe\u0142czyk, A., Perlejewski, K., and Osuch, S. (2022). Higher Immunological Response after BNT162b2 Vaccination among COVID-19 Convalescents-The Data from the Study among Healthcare Workers in an Infectious Diseases Center. Vaccines, 10.","DOI":"10.3390\/vaccines10122158"},{"key":"ref_54","first-page":"250","article-title":"Immunogenicity and effectiveness of BNT162b2 COVID-19 vaccine in a cohort of healthcare workers in Milan (Lombardy Region, Northern Italy)","volume":"46","author":"Consonni","year":"2022","journal-title":"Epidemiol. Prev."},{"key":"ref_55","doi-asserted-by":"crossref","unstructured":"Augustinussen, M.H., Tylden, G.D., and Rinaldo, C.H. (2023). Dynamics of SARS-CoV-2 Spike-IgG throughout Three COVID-19 Vaccination Regimens: A 21-Month Longitudinal Study of 82 Norwegian Healthcare Workers. Viruses, 15.","DOI":"10.3390\/v15030619"},{"key":"ref_56","doi-asserted-by":"crossref","first-page":"145","DOI":"10.2147\/JIR.S394760","article-title":"The Levels of Anti-SARS-CoV-2 Spike Protein IgG Antibodies Before and After the Third Dose of Vaccination Against COVID-19","volume":"16","author":"Starz","year":"2023","journal-title":"J. Inflamm. Res."},{"key":"ref_57","doi-asserted-by":"crossref","first-page":"1136","DOI":"10.3390\/vaccines11071136","article-title":"A Serological Analysis of the Humoral Immune Responses of Anti-RBD IgG, Anti-S1 IgG, and Anti-S2 IgG Levels Correlated to Anti-N IgG Positivity and Negativity in Sicilian Healthcare Workers (HCWs) with Third Doses of the mRNA-Based SARS-CoV-2 Vaccine: A Retrospective Cohort Study","volume":"11","author":"Serra","year":"2023","journal-title":"Vaccines"},{"key":"ref_58","doi-asserted-by":"crossref","first-page":"40","DOI":"10.1186\/s13027-022-00451-1","article-title":"Bimodal antibody-titer decline following BNT162b2 mRNA anti-SARS-CoV-2 vaccination in healthcare workers of the INT\u2014IRCCS \u201cFondazione Pascale\u201d Cancer Center (Naples, Italy)","volume":"17","author":"Russo","year":"2022","journal-title":"Infect. Agents Cancer"},{"key":"ref_59","doi-asserted-by":"crossref","unstructured":"Sarrigeorgiou, I., Moschandreou, D., Dimitriadis, A., Tsinti, G., Sotiropoulou, E., Ntoukaki, E., Eliadis, P., Backovic, M., Labropoulou, S., and Escriou, N. (2022). Combined monitoring of IgG and IgA anti-Spike and anti-Receptor binding domain long term responses following BNT162b2 mRNA vaccination in Greek healthcare workers. PLoS ONE, 17.","DOI":"10.1371\/journal.pone.0277827"},{"key":"ref_60","doi-asserted-by":"crossref","first-page":"12716","DOI":"10.1038\/s41598-022-16759-2","article-title":"Immunogenicity evaluation after BNT162b2 booster vaccination in healthcare workers","volume":"12","author":"Zurac","year":"2022","journal-title":"Sci. Rep."},{"key":"ref_61","doi-asserted-by":"crossref","first-page":"311","DOI":"10.5114\/ceji.2023.134250","article-title":"COVID-19 vaccination in healthcare workers: Long-term benefits and protection","volume":"48","author":"Szczepanek","year":"2023","journal-title":"Cent. Eur. J. Immunol."},{"key":"ref_62","doi-asserted-by":"crossref","unstructured":"Klein, S.L., and Roberts, C. (2010). Sex Steroid Receptors in Immune Cells. Sex Hormones and Immunity to Infection, Springer.","DOI":"10.1007\/978-3-642-02155-8"},{"key":"ref_63","doi-asserted-by":"crossref","first-page":"2273697","DOI":"10.1080\/21645515.2023.2273697","article-title":"Association between sex hormones and anti-S\/RBD antibody responses to COVID-19 vaccines in healthcare workers","volume":"19","author":"Anticoli","year":"2023","journal-title":"Hum. Vaccines Immunother."},{"key":"ref_64","doi-asserted-by":"crossref","first-page":"578","DOI":"10.3892\/mmr.2021.12217","article-title":"COVID-19 vaccination and IgG and IgA antibody dynamics in healthcare workers","volume":"24","author":"Zurac","year":"2021","journal-title":"Mol. Med. Rep."},{"key":"ref_65","doi-asserted-by":"crossref","first-page":"e1915983","DOI":"10.1001\/jamanetworkopen.2019.15983","article-title":"Comparison of Cardiovascular Risk Factors and Outcomes Among Practicing Physicians vs the General Population in Ontario, Canada","volume":"2","author":"Ko","year":"2019","journal-title":"JAMA Netw. Open"},{"key":"ref_66","doi-asserted-by":"crossref","unstructured":"Collatuzzo, G., Visci, G., Violante, F.S., Porru, S., Spiteri, G., Monaco, M.G.L., Fillon, F.L., Negro, C., Janke, C., and Castelletti, N. (2022). Determinants of anti-S immune response at 6 months after COVID-19 vaccination in a multicentric European cohort of healthcare workers\u2014ORCHESTRA project. Front. Immunol., 13.","DOI":"10.3389\/fimmu.2022.986085"}],"container-title":["Medicina"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1648-9144\/62\/5\/810\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,4,26]],"date-time":"2026-04-26T04:11:12Z","timestamp":1777176672000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1648-9144\/62\/5\/810"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,4,24]]},"references-count":66,"journal-issue":{"issue":"5","published-online":{"date-parts":[[2026,5]]}},"alternative-id":["medicina62050810"],"URL":"https:\/\/doi.org\/10.3390\/medicina62050810","relation":{},"ISSN":["1648-9144"],"issn-type":[{"value":"1648-9144","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,4,24]]}}}