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Although the anti-COVID-19 vaccination has proved to be an effective preventive tool, "breakthrough infections" have been documented in patients with complete primary vaccination courses. Most of the SARS-CoV-2 neutralizing antibodies produced after SARS-CoV-2 infection target the spike protein receptor-binding domain which has an important role in facilitating viral entry and the infection of the host cells. SARS-CoV-2 has demonstrated the ability to evolve by accumulating mutations in the spike protein to escape the humoral response of a host. The aim of this study was to compare the titers of neutralizing antibodies (NtAbs) against the variants of SARS-CoV-2 by analyzing the sera of recovered and vaccinated healthcare workers (HCWs). A total of 293 HCWs were enrolled and divided into three cohorts as follows: 91 who had recovered from SARS-CoV-2 infection (nVP); 102 that were vaccinated and became positive after the primary cycle (VP); and 100 that were vaccinated with complete primary cycles and concluded the follow-up period without becoming positive (VN). Higher neutralization titers were observed in the vaccinated subjects' arms compared to the nVP subjects' arms. Differences in neutralization titers between arms for single variants were statistically highly significant ( p < 0.001), except for the differences between titers against the Alpha variant in the nVP and in VP groups, which were also statistically significant ( p < 0.05). Within the nVP group, the number of subjects with an absence of neutralizing antibodies was high. The presence of higher titers in patients with a complete primary cycle compared to patients who had recovered from infection suggested the better efficacy of artificial immunization compared to natural immunization, and this further encourages the promotion of vaccination even in subjects with previous infections., Competing Interests: The authors declare no conflict of interest.

Suboptimal levels of measles vaccination coverage make Italy a country where the circulation of the virus is still endemic. In the past decade, several nosocomial outbreaks of measles occurred in Italy that rapidly spread the infection among large numbers of hospitalized patients and susceptible healthcare workers (HCWs). A cross-sectional study was conducted at the University Hospital of Palermo (Italy) to estimate the rate of HCWs immunization and to investigate the factors associated with lack of immunization. The attitude to the immunization practice was evaluated by exploring the Health Belief Model. Overall, 118 HCWs were enrolled, with a mean age of 31 years and 59.3% male. About half of the sample (45.8%, n = 54) was found not to be immunized against measles. Multivariable analysis showed that the factors directly associated with the non-immunization status against measles were female sex (OR = 3.70, p = 0.056), being an HCW different from a physician (OR = 10.27, p = 0.015), having a high perception of barriers to vaccination (OR = 5.13, p = 0.047), not being immunized for other exanthematous diseases such as chickenpox (OR = 9.93, p = 0.003), mumps (OR = 33.64, p < 0.001) and rubella (OR = 10.12, p = 0.002). There is a need to contrast the low adherence of HCWs to measles vaccination by identifying effective strategies to increase immunization coverage and limiting the risk of further nosocomial measles outbreaks.

In order to determine the humoral protective response against SARS-CoV-2, the vaccine-induced and naturally induced neutralizing antibodies (NtAbs) responses against SARS-CoV-2 variants circulating in Italy through in vitro live virus neutralization assay were evaluated. A total of 39 SARS-CoV-2 recovered subjects (COVID-19+) and 63 subjects with a two-dose cycle of the BNT16262 vaccine were enrolled. A single serum sample was tested for COVID-19+ at 35-52 days post-positive swab, while vaccinees blood samples were taken at one (V1) and at three months (V3) after administration of the second vaccine dose. Significantly higher NtAb titers were found against B.1 and Alpha in both COVID-19+ and vaccinees, while lower NtAb titers were detected against Delta, Gamma, and Omicron variants. A comparison between groups showed that NtAb titers were significantly higher in both V1 and V3 than in COVID-19+, except against the Omicron variant where no significant difference was found. COVID-19+ showed lower neutralizing titers against all viral variants when compared to the vaccinees. Two-dose vaccination induced a sustained antibody response against each analyzed variant, except for Omicron. The evolution process of SARS-CoV-2, through variants originating from an accumulation of mutations, can erode the neutralizing effectiveness of natural and vaccine-elicited immunity. Therefore, a need for new vaccines should be evaluated to contain the ongoing pandemic.

COVID-19 is a current global threat, and the characterization of antibody response is vitally important to update vaccine development and strategies. In this study we assessed SARS-CoV-2 antibody concentrations in SARS-CoV-2 positive patients (N = 272) and subjects vaccinated with the BNT162b2 m-RNA COVID-19 vaccine (N = 1256). For each participant, socio-demographic data, COVID-19 vaccination records, serological analyses, and SARS-CoV-2 infection status were collected. IgG antibodies against S1/S2 antigens of SARS-CoV-2 were detected. Almost all vaccinated subjects (99.8%) showed a seropositivity to anti-SARS-COV-2 IgG and more than 80% of vaccinated subjects had IgG concentrations > 200 AU/mL. In a Tobit multivariable regression analysis, SARS-CoV-2 vaccination was statistically significantly associated with increased IgG concentrations (β coef = 266.4; p < 0.001). A statistically significant reduction in SARS-CoV-2 IgG concentrations was found with older age (β coef = -1.96 per year increase; p < 0.001), male sex (β coef = -22.3; p < 0.001), and days after immunization (β coef = -1.67 per day increase; p < 0.001). Our findings could support the vaccination campaigns confirming the high immunogenicity of the SARS-CoV-2 vaccine under investigation with respect to the natural infection. Further studies will be required for evaluating the role of age and days after immunization in the persistence of vaccine antibodies and protection from the disease.