AUTHOR=Collatuzzo Giulia , De Palma Giuseppe , Violante Francesco S. , Porru Stefano , Larese Filon Francesca , Fabianova Eleonora , Violán Concepción , Vimercati Luigi , Leustean Mihaela , Rodriguez-Suarez Marta Maria , Sansone Emanuele , Sala Emma , Zunarelli Carlotta , Lodi Vittorio , Monaco Maria Grazia Lourdes , Spiteri Gianluca , Negro Corrado , Beresova Jana , Carrasco-Ribelles LucÌa A. , Tafuri Silvio , Asafo Shuffield S. , Ditano Giorgia , Abedini Mahsa , Boffetta Paolo 

TITLE=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

JOURNAL=Frontiers in Immunology

VOLUME=Volume 13 - 2022

YEAR=2023

URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2022.1079884

DOI=10.3389/fimmu.2022.1079884

ISSN=1664-3224

ABSTRACT=Background: Persistence of vaccine immunization is key for COVID-19 prevention.

Methods:  We investigated the difference between two serological measurement of anti-COVID-19 S1 antibodies in an individual-level analysis on 19,422 vaccinated healthcare workers (HCW) from Italy, Spain, Romania and Slovakia, tested within 13 months from first dose. Differences in serological level were divided by the standard error of the cohort-specific distribution, obtaining standardized measurements. We fitted multivariate linear regression models to identify predictors of difference between two measurements.

Results: We observed a progressively reduced difference from <30 days to 210-240 days. Age was associated with increased difference. HCW infected between the two serological measurements had a greater difference compared to the never infected; the infected before the first measurement had a relative risk [RR] of 0.81 for one standard deviation in the difference (95% confidence interval [CI] 0.78-0.85).  The RR for a 30-day increase in time between first dose and first serology, and between the two serologies, were  1.08 (95% CI 1.07-1.10) and 1.04 (95% CI 1.03-1.05). The first measurement was a strong predictor of the subsequent antibody decrease (RR 1.60; 95% CI 1.56-1.64). Compared to Comirnaty, Spikevax (RR 0.83, 95% CI=0.75-0.92) and mixed vaccines (RR 0.61; 95% 0.51-0.74) were associated to a smaller decrease. Third vaccine dose was associated with smaller decrease (RR 0.46; 95% CI 0.40-0.54).

Conclusions: Age, COVID-19 infection, number of doses, time between first dose and first serology, time between serologies and type of vaccine were associated to difference between two serological measurements within a 13-month period.