Search

Introduction: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV2), the causative agent of coronavirus disease 2019 (COVID19), has led to a global pandemic. Currently, the diagnosis of COVID-19 is confirmed by detecting SARS-CoV-2 via RealTime-RT-PCR in rhino-pharyngeal swab. Serological test is required to evaluate a previous exposure to the virus, as well as antibody response. The aim of this multicentric study is to analyse the antibody response following COVID-19 vaccination in healthcare workers and guests of nursing homes, and to determine differences between subjects with or without a confirmed previous infection. Methods: Our study included 657 subjects, recruited from guests and healthcare workers of nursing homes in the Piedmont region. 10 days after the completion of the vaccination cycle, a blood sample was taken from the subjects to measure IgG against SARS-CoV-2 spike protein. Serological testing was performed using an enzyme immunoassay kit (EUROIMMUN AntiSARS-CoV-2 QuantiVac ELISA). We performed statistical analysis with R software. Results: We recruited 657 subjects aged between 19 to 106. Among them, 404 had a previous infection and 253 didn’t have a known previous infection. The serological examination resulted positive in 655 subjects and negative in 2 (X IgG 1095 RU/ml). Samples with titer> 1200 RU/ml will be further diluted to identify the titer and differences from the baseline situation. Conclusions: This study analyses neutralizing antibodies, which should prevent the virus from binding to target cells via spike protein. According to literature, immunological response to vaccine presents a great variability of antibodies level in the study population. However, no significantly correlations were found between the available variables. Preliminary data show the presence of a very intense antibody response after active vaccine immunization both in subjects with previous infection and in the rest of the study population. Key messages: Covid-19 vaccine response in a population at risk. Differences between subjects with or without a confirmed previous infection. [ABSTRACT FROM AUTHOR]

Introduction: Studies on the duration of immune response in subjects with COVID-19 could facilitate understanding of how immunity develops and persists during the natural course of infection, as well as providing epidemiological information useful in public health decisions on the use of vaccines. The study aims to analyse antibody response in a cohort of subjects with highrisk of exposure to SARS-CoV-2 due to the long-term care facility environment. Methods: We recruited 657 subjects between guests and healthcare workers from Piedmontese nursing homes. IgG directed against the S1 domain of SARS-CoV-2 spike protein were assayed on serum. We used EUROIMMUN kit, which exploits ELISA method. Reference values are (RU/mL): positive 11; borderline 8 ] value < 11; negative < 8. Results: Among the 657 subjects, we examined 494 health workers and 163 guests. The average age was 56.2. In relation to COVID-19, 402 subjects had a previous infection, 255 had not. About serology: positive 369; negative 261; borderline 27. The mean of the IgG values was 35.68 RU/mL. Swabs/serology: 77.36% with previous infection were positive to serology, 18.66% negative; of all subjects who were always negative to swabs, 72.94% were negative, 22.74% positive. Moreover, the mean time elapsed from positive swab to serology test was 144.08 days. Conclusions: Preliminary results show that the antibody response is present and persistent in the study population, even a long time after the infection. According to literature, antibody persistence has great variability in our population, as no statistically significant correlations were found between antibody titer and other variables such as time elapsed since infection. The examined sample, belonging to high-risk category (long-term care facilities), is most likely to present repeated exposure to SARS-CoV-2, highlighted by the seropositivity of never infected subjects. These findings might help policy makers better address resources regarding vaccines. Key messages: Antibody response is present and persistent in the study population, even a long time after the infection. Antibody persistence has great variability in our population, as no statistically significant correlations were found between antibody titer and other variables such as time elapsed since infection. [ABSTRACT FROM AUTHOR]