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The successful deployment of safe and effective vaccines against coronavirus disease 2019 (COVID-19) has been crucial in reducing the global disease burden. Owing to the need for vaccination series over time, continuous observational studies are needed to estimate the COVID-19 vaccine response in real-world conditions. In particular, the detection, assessment, and understanding of adverse effects following immunization (AEFI) with a COVID-19 vaccine are crucial to better address vaccination strategies. Therefore, this study aimed to investigate the risk of repeated AEFI post-administration of a booster dose of mRNA COVID-19 vaccine in a sample of healthcare workers (HCWs) in an Italian teaching hospital. The data on any local and systemic AEFI were studied in multivariate Poisson regression analyses to model the association between the incidence of each postvaccination symptom and its prior reporting after the administration of the previous doses. Overall, compared with the primary vaccination series, the majority of post-third dose AEFI were less reported. The results from multivariable models showed that the likelihood of reporting an AEFI after the third dose was higher in those who experienced the same postvaccination symptom after the second dose (all AEFI except for itch at injection site) and, although not significant for all AEFI, after the first dose. Any associations with age, gender, smoking habits, previous SARS-CoV-2 infection and other characteristics, as well as the health impact of AEFI were also assessed. Taken together, the results from this research support reframe AEFI symptoms as signals of a robust postvaccination reaction as well as of common vaccine response, and they add important data to inform booster vaccination strategies in HCWs and, extensively, in the adult population. [ABSTRACT FROM AUTHOR]

This longitudinal observational study investigated the risk of breakthrough SARS-CoV-2 infection up to 6 months after a booster dose of an mRNA COVID-19 vaccine in infection-naïve vs. previously infected healthcare workers (HCWs), and whether this difference varied over time. A Cox proportional hazard regression model with Aalen's additive analysis was fitted to examine the association between the risk of infections and predictor variables. Overall, we observed an incidence rate of 2.5 cases per 1000 person-days (95% confidence interval [CI] 2.0–3.0), which dropped at 0.8 per 1000 person-days (95% CI 0.3–2.0) in recipients with prior SARS-CoV-2 infection. The fitted analysis indicated an adjusted hazard ratio of 0.32 (95% CI 0.13–0.80; p-value = 0.01) for those with hybrid immunity with a slope that became steeply negative roughly starting from day 90. No difference was seen according to participants' smoking habits. Characteristics of infected HCWs were also described. Our study quantifies the time-varying effects of vaccine-induced and hybrid immunity after the booster dose (during the Omicron variant predominance in Italy) and observed that the protection waned more rapidly in infection-naïve recipients starting from the third month. The results add important evidence that can be used to inform COVID-19 vaccination strategies. [ABSTRACT FROM AUTHOR]

Keywords: Pfizer COVID-19 vaccine; SARS-CoV-2; S-RBD-specific; immunoglobulins; seroconversion; decreasing immunity; neutralizing antibodies EN Pfizer COVID-19 vaccine SARS-CoV-2 S-RBD-specific immunoglobulins seroconversion decreasing immunity neutralizing antibodies 1 3 3 01/05/22 20211201 NES 211201 Research letter Emerging evidence is offering significant insights into the effectiveness and safety of the vaccination against the Coronavirus Disease 2019 (COVID-19), but another crucial aspect of the current global vaccination campaign is the time trend of the antibody response to COVID-19 vaccines over a longer period and the resulting duration of the protection offered.1 Here, we present data on the dynamics of antibodies that bind SARS-CoV-2 spike (S) protein receptor binding domain (RBD) - the most critical target for SARS-CoV-2-specific antibodies within the S1 sub-unit2 - after 6 months from the administration with BNT162b2 vaccine. Pfizer COVID-19 vaccine, SARS-CoV-2, S-RBD-specific, immunoglobulins, seroconversion, decreasing immunity, neutralizing antibodies Complete methods of the VASCO project have been presented elsewhere.3 In this survey, HCWs who were administered the two-dose BNT162b2 mRNA vaccine 21 days apart between December 2020 and January 2021 were invited to undertake a quantitative serology test for the research of SARS-CoV-2 S-RBD-specific immunoglobulins G (IgG). [Extracted from the article]