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Although the HIV epidemic in Athens, Greece has reemerged and spread in men who have sex with men (MSM), state-supported PrEP programs have not been instituted. A PrEP intervention was implemented building upon an existing network cohort of MSM (308 participants; 1212 network members). A PrEP intervention cohort of 106 participants was selected based upon sex behaviors. Individual, partner, and network characteristics were compared between the cohorts. The PrEP cohort members were more highly connected and in more influential positions in the network than their peers. Further, their sexual network connections’ behaviors increased their vulnerability to HIV infection relative to the rest of the network’s sex partners. This included greater stimulant use (24.2% vs 7.0%; χ2 = 28.2; p < 0.001), greater rates of at least weekly condomless sex (OR = 2.7; 95% CI 2.1–3.5; χ2 = 59.2; p < 0.001) and at least weekly use of drugs or alcohol during sex (OR = 3.4; 95% CI 2.6–4.3; χ2 = 89.7; p < 0.001). Finally the PrEP cohort’s social networks showed similarly increased vulnerability to seroconversion, including greater rates of injection drug use (4.1% vs 0.5%; χ2 = 3.9; p = 0.04), greater stimulant use (33.6% vs 14.6%; χ2 = 16.9, p < 0.001), and higher rates of recent STIs (21.6% vs 13.1%; χ2 = 4.4; p = 0.04). Thus, this PrEP intervention engaged individuals in vulnerable positions with vulnerable connections within an MSM community. © 2022, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.

Several lines of evidence suggest that binding SARS-CoV-2 antibodies such as anti-SARSCoV-2 RBD IgG (anti-RBD) and neutralising antibodies (NA) are correlates of protection against SARS-CoV-2, and the correlation of anti-RBD and NA is very high. The effectiveness (VE) of BNT162b2 in preventing SARS-CoV-2 infection wanes over time, and this reduction is mainly associated with waning immunity, suggesting that the kinetics of antibodies reduction might be of interest to predict VE. In a study of 97 health care workers (HCWs) vaccinated with the BNT162b2 vaccine, we assessed the kinetics of anti-RBD 30–250 days after vaccination using 388 individually matched plasma samples. Anti-RBD levels declined by 85%, 92%, and 95% at the 4th, 6th, and 8th month from the peak, respectively. The kinetics were estimated using the trajectories of anti-RBD by various models. The restricted cubic splines model had a better fit to the observed data. The trajectories of anti-RBD declines were statistically significantly lower for risk factors of severe COVID-19 and the absence of vaccination side effects. Moreover, previous SARS-CoV-2 infection was associated with divergent trajectories consistent with a slower anti-RBD decline over time. These results suggest that anti-RBD may serve as a harbinger for vaccine effectiveness (VE), and it should be explored as a predictor of breakthrough infections and VE. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.

Background: Understanding the factors that affect the transmissibility of SARS-CoV-2 remains important to keep transmission low and maximize the health benefits of vaccination. We assessed the factors associated with the transmissibility of SARS-CoV-2 based on contact tracing data. Methods: From 1 October to 9 December 2020, 29,385 laboratory-confirmed SARS-CoV-2 cases (index cases, i.e. the first identified laboratory-confirmed cases or with the earliest symptom onset in a setting) and 64,608 traced contacts were identified in Greece. We assessed the prevalence of symptoms in cases, calculated secondary attack rates and assessed factors associated with infectivity and susceptibility to infection. Results: There were 11,232 contacts secondarily infected (secondary attack rate: 17.4%, 95% CI:17.0–17.8). Contacts aged 0–11 and 12–17 years were less susceptible to infection than adults 65 years or older (odds ratio (OR) [95% CI]: 0.28 [0.26–0.32] and 0.44 [0.40–0.49], respectively). Index cases aged 65 years or older were more likely to infect their contacts than other adults or children/adolescents. The odds of infection [95% CI] were higher in contacts exposed within the household (1.71 [1.59–1.85] vs. other) and in cases with cough (1.17 [1.11–1.25] vs. no cough). There was an interaction between the age of the index and the age of the contact with contacts 65 years or older having a higher probability of infection when exposed to cases of similar age than to children. Conclusions: Our findings highlight the role of age and age mixing in infectivity and susceptibility to SARS-CoV-2 infection. Precautions are necessary for individuals 65 or older as they have higher infectivity and susceptibility in contact with their peers. © 2021 Society for Scandinavian Journal of Infectious Diseases.

Due to their higher risk of developing life-threatening COVID-19 disease, solid organ transplant (SOT) recipients have been prioritized in the vaccination programs of many countries. However, there is increasing evidence of reduced immunogenicity to SARS-CoV-2 vaccination. The present study investigated humoral response, safety, and effectiveness after the two mRNA vaccines in 455 SOT recipients. Overall, the antibody response rate was low, at 39.6%. Higher immunogenic-ity was detected among individuals vaccinated with the mRNA1273 compared to those with the BNT162b2 vaccine (47% vs. 36%, respectively, p = 0.025) as well as higher median antibody levels of 31 (7, 372) (AU/mL) vs. 11 (7, 215) AU/mL, respectively. Among the covariates assessed, vaccination with the BNT162b2 vaccine, antimetabolite-and steroid-containing immunosuppression, female gender, the type of transplanted organ and older age were factors that negatively influenced immune response. Only mild adverse effects were observed. Our findings confirm poor immunogenicity after vaccination, implicating a reevaluation of vaccination policy in SOT recipients. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.

Vaccine hesitancy is a major barrier to achieving large-scale COVID-19 vaccination. We report trends in vaccination intention and associated determinants from surveys in the adult general population in Greece. Four cross-sectional phone surveys were conducted in November 2020 and February, April and May 2021 on nationally representative samples of adults in Greece. Multino-mial logistic regression was used on the combined data of the surveys to evaluate independent predictors of vaccination unwillingness/uncertainty. Vaccination intention increased from 67.6% in November 2020 to 84.8% in May 2021. Individuals aged 65 years or older were more willing to be vaccinated (May 2021: 92.9% vs. 79.5% in 18–39 years, p < 0.001) but between age-groups differences decreased over time. Vaccination intention increased substantially in both men and women, though earlier among men, and was higher in individuals with prograduate education (May 2021: 91.3% vs. 84.0% up to junior high). From multivariable analysis, unwillingness and/or uncertainty to be vaccinated was associated with younger age, female gender (in particular in the April 2021 survey), lower educational level and living with a child ≤12 years old. Among those with vaccine hesitancy, concerns about vaccine effectiveness declined over time (21.6% in November 2020 vs. 9.6% in May 2021, p = 0.014) and were reported more often by men; safety concerns remained stable over time (66.3% in November 2020 vs. 62.1% in May 2021, p = 0.658) and were reported more often by women. In conclusion, vaccination intention increased substantially over time. Tailored communication is needed to address vaccine hesitancy and concerns regarding vaccine safety. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.

BNT162b2 has proven to be highly effective, but there is a paucity of data regarding immunogenicity factors and comparison between response to vaccination and natural infection. This study included 871 vaccinated healthcare workers (HCW) and 181 patients with natural infection. Immunogenicity was assessed by measuring anti-SARS-CoV-2 against the RBD domain of the spike protein (anti-RBD). Samples were collected 1–2 weeks after vaccination or 15–59 days post-onset of symptoms. Post-vaccine anti-RBD concentrations were associated with age, gender, vaccination side-effects (VSE) and prior infection (Pr-CoV). Anti-RBD median levels (95%CI) were lower by 2466 (651–5583), 6228 (3254–9203) and 7651 (4479–10,823) AU/mL in 35–44, 45–54, 55–70 yrs, respectively, compared with the 18–34 yrs group. In females, the median levels were higher by 2823 (859–4787), 5024 (3122–6926) in individuals with VSE, and 9971 (5158–14,783) AU/mL in HCWs with Pr-CoV. The ratio of anti-RBD in vaccinated individuals versus those with natural infection varied from 1.0 to 19.4. The high immunogenicity of BNT162b2 is verified, although its sustainability has yet to be elucidated. The use of comparative data from natural infection serological panels, expressing the clinical heterogeneity of natural infection, may facilitate early decisions for candidate vaccines to be evaluated in clinical trials. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

Nearly half the new HIV infections in Greece occur in sexual minority men, yet pre-exposure prophylaxis is not currently supported in the national HIV program. We examined factors associated with PrEP persistence among Greek SMM in PrEP for Greece, the first PrEP study in Greece. Participants (n = 100) were recruited from 2016 to 2018 through respondent-driven sampling among SMM in Athens, receiving supplies for daily PrEP at interval visits over 12-months. PrEP persistence, operationalized as Total PrEP Time, was high, 74% of participants achieving perfect persistence. Higher alcohol risk scores (OR 1.27, 95% CI 1.08–1.49) and adherence to HIV testing guidelines (OR 1.23, 95% CI 1.00–1.51) were associated with persistence. Housing impermanence (OR 0.14, 95% CI 0.04–0.48) and serostatus disclosure concerns (OR 0.77, 95% CI 0.60–0.97) were associated with limited PrEP persistence. While PrEP persistence among Greek SMM is high, socioeconomic factors and societal attitudes may challenge prevention efforts. © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.

Objective: To measure the prevalence of food insecurity and explore related characteristics and behaviours among people who inject drugs (PWID). Design: Cross-sectional analysis of a community-based programme for HIV infection among PWID (ARISTOTLE programme). Food insecurity was measured by the Household Food Insecurity Access Scale. Computer-assisted interviews and blood samples were also collected. Setting: A fixed location in Athens Metropolitan Area, Greece, during 2012-2013. Participants: In total, 2834 unique participants with history of injecting drug use in the past 12 months were recruited over four respondent-driven sampling rounds (approximately 1400/round). Results: More than 50 % of PWID were severely or moderately food insecure across all rounds. PWID were more likely to be severely food insecure if they were older than 40 years [adjusted OR (aOR): 1.71, 95 % CI: 1.33-2.19], were women (aOR: 1.49, 95 % CI: 1.17-1.89), from Middle East countries (aOR v. from Greece: 1.80, 95 % CI: 1.04-3.11), had a lower educational level (primary or secondary school v. higher education; aOR: 1.54, 95 % CI: 1.29-1.84), had no current health insurance (aOR: 1.45, 95 % CI: 1.21-1.73), were homeless (aOR: 17.1, 95 % CI: 12.3-23.8) or were living with another drug user (aOR: 1.55, 95 % CI: 1.26-1.91) as compared with those living alone or with family/friends. HIV-infected PWID were more likely to be severely food insecure compared with uninfected (59.0 % v. 51.0 %, respectively, P = 0.002); however, this difference was attributed to the confounding effect of homelessness. Conclusions: Moderate/severe food insecurity was a significant problem, reaching > 50 % in this sample of PWID and closely related to socio-demographic characteristics and especially homelessness. © Authors 2020.

Background: Improving HIV diagnosis, access to care and effective antiretroviral treatment provides our global strategy to reduce HIV incidence. To reach this goal we need to increase our knowledge about local epidemics. HIV infection dates would be an important information towards this goal, but they are largely unknown. To date, methods to estimate the dates of HIV infection are based mainly on laboratory or molecular methods. Our aim was to validate molecular clock inferred infection dates that were estimated by analysing sequences from 145 people living with HIV (PLHIV) with known transmission dates (clinically estimated infection dates). Methods: All HIV sequences were obtained by Sanger sequencing and were previously found to belong to well-established molecular transmission clusters (MTCs). Results: Our analysis showed that the molecular clock inferred infection dates were correlated with the clinically estimated ones (Spearman's Correlation coefficient = 0.93, p < 0.001) and that there was an agreement between them (Lin's concordance correlation coefficient = 0.92, p < 0.001). For the 61.4% of cases the molecular clock inferred preceded the clinically estimated infection dates. The median difference between clinically and molecularly estimated dates of infection was of 0.18 (IQR: −0.21, 0.89) years. The lowest differences were identified in people who inject drugs of our study population. Conclusions: The estimated time to more recent common ancestor (tMRCA) of nodes within clusters provides a reliable approximation of HIV infections for PLHIV infected within MTCs. Next-generation sequencing data and molecular clock estimates based on heterochronous sequences provide, probably, more reliable methods for inferring infection dates. However, since these data are not available in most of the HIV clinical laboratories, our approach, under specific conditions, can provide a reliable estimation of HIV infection dates and can be used for HIV public health interventions. © 2021 Elsevier B.V.

Greece imposed a nationwide lockdown in March 2020 to mitigate transmission of severe acute respiratory syndrome coronavirus 2 during the first epidemic wave. We conducted a survey on age-specific social contact patterns to assess effects of physical distancing measures and used a susceptible-exposed-infectious-recovered model to simulate the epidemic. Because multiple distancing measures were implemented simultaneously, we assessed their overall effects and the contribution of each measure. Before measures were implemented, the estimated basic reproduction number (R0) was 2.38 (95% CI 2.01-2.80). During lockdown, daily contacts decreased by 86.9% and R0 decreased by 81.0% (95% credible interval [CrI] 71.8%-86.0%); each distancing measure decreased R0 by 10%-24%. By April 26, the attack rate in Greece was 0.12% (95% CrI 0.06%-0.26%), one of the lowest in Europe, and the infection fatality ratio was 1.12% (95% CrI 0.55%-2.31%). Multiple social distancing measures contained the first epidemic wave in Greece. © 2021 Centers for Disease Control and Prevention (CDC). All rights reserved.

Introduction Greece is a country with limited spread of SARS-CoV-2 and cumulative infection attack rate of 0.12% (95% CI 0.06–0.26). Health care workers (HCWs) are a well-recognized risk group for COVID-19. The study aimed to estimate the seroprevalence of antibodies to SARS-CoV-2 in a nosocomial setting and assess potential risk factors. Methods HCWs from two hospitals participated in the study. Hospital-1 was a tertiary university affiliated center, involved in the care of COVID-19 patients while hospital-2 was a tertiary specialized cardiac surgery center not involved in the care of these patients. A validated, CE, rapid, IgM/IgG antibody point-of-care test was used. Comparative performance with a reference globally available assay was assessed. Results 1,495 individuals consented to participate (response rate 77%). The anti-SARS-CoV-2 weighted prevalence was 1.26% (95% CI 0.43, 3.26) overall and 0.53% (95% CI 0.06, 2.78) and 2.70% (95% CI 0.57, 9.19) in hospital-1 and hospital-2, respectively although the study was underpowered to detect statistically significant differences. The overall, hospital-1, and hospital-2 seroprevalence was 10, 4 and 22 times higher than the estimated infection attack rate in general population, respectively. Suboptimal use of personal protective equipment was noted in both hospitals. Conclusions These data have implications for the preparedness of a second wave of COVID-19 epidemic, given the low burden of SARS-CoV-2 infection rate, in concordance with national projections. © 2020 Psichogiou et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.