Is mandatory vaccination in population over 60 adequate to control the COVID-19 pandemic in E.U.?

Vaccine hesitancy, which potentially leads to refusal or delayed acceptance of COVID-19 vaccines, is considered a key driver for the increasing death toll from the pandemic in the E.U.. European Commission and several member states governments are either planning or have already directly or indirectly announced mandatory vaccination for individuals aged over 60, the group repeatedly proved to be the most vulnerable. In this paper, an assessment of this strategy benefits is attempted. This is done by examining the reduction of Standard Expected Years of Life Lost (SEYLL) per person of the EU population over 60 as a function of their vaccination percentage. Publicly available data and some first results of the second iteration of the SHARE COVID-19 survey conducted during the summer of 2021 on acceptance of COVID-19 vaccines are used as input.

Relating SARS-CoV-2 shedding rate in wastewater to daily positive tests data: A consistent model based approach

During the COVID-19 pandemic, wastewater-based epidemiology (WBE) has been engaged to complement medical surveillance and in some cases to also act as an early diagnosis indicator of viral spreading in the community. Most efforts worldwide by the scientific community and commercial companies focus on the formulation of protocols for SARS CoV-2 analysis in wastewater and approaches addressing the quantitative relationship between WBE and medical surveillance are lacking. In the present study, a mathematical model is developed which uses as input the number of daily positive medical tests together with the highly non-linear shedding rate curve of individuals to estimate the evolution of virus shedding rate in wastewater along calendar days. A comprehensive parametric study by the model using as input actual medical surveillance and WBE data for the city of Thessaloniki ([~]700,000 inhabitants, North Greece) during the outbreak of November 2020 reveals the conditions under which WBE can be used as an early warning tool for predicting pandemic outbreaks. It is shown that early warning capacity is different along the days of an outbreak and depends strongly on the number of days apart between the day of maximum shedding rate of infected individuals in their disease cycle and the day of their medical testing. The present data indicate for Thessaloniki an average early warning capacity of around 2 days. Moreover, the data imply that there exists a proportion between unreported cases (asymptomatic persons with mild symptoms that do not seek medical advice) and reported cases. The proportion increases with the number of reported cases. The early detection capacity of WBE improves substantially in the presence of an increasing number of unreported cases. For Thessaloniki at the peak of the pandemic in mid-November 2020, the number of unreported cases reached a maximum around 4 times the number of reported cases. HIGHLIGHTSO_LIModel estimates viral load evolution in wastewater from infected people dynamics C_LIO_LIIdentifying actual conditions for which WBE can be used as an early warning tool C_LIO_LIEarly warning capacity increases with an increasing number of unreported cases C_LIO_LIIn Thessaloniki Nov20 outbreak, the early warning capacity of WBE was about 2 days C_LIO_LIIn Thessaloniki Nov20 outbreak, unreported cases were up to 4 times reported cases C_LI

Trends in COVID-19 vaccination intent, determinants and reasons for vaccine hesitancy: results from repeated cross-sectional surveys in the adult general population of Greece during November 2020-June 2021

BackgroundVaccine hesitancy is a major barrier to achieve large-scale COVID-19 vaccination. We report trends in vaccination intention and associated determinants from surveys in the adult general population in Greece. MethodsFour cross-sectional phone surveys were conducted in November 2020, February, April and May 2021 on nationally representative samples of adults in Greece. Multinomial logistic regression was used on the combined data of the surveys to evaluate independent predictors of vaccination unwillingness/uncertainty. ResultsVaccination intention increased from 67.6% in November 2020 to 84.8%. in May 2021. Individuals aged 65 years or older were more willing to get 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 sexes, though earlier among men than women and was higher in individuals with postgraduate studies (May 2021: 91.3% vs. 84.0% up to junior high). From multivariable analysis, unwillingness and/or uncertainty to get 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. ConclusionsVaccination intention increased substantially over time. Tailored communication is needed to address vaccine hesitancy and concerns regarding vaccine safety. FundingThe phone surveys were conducted with the kind support of the Greek Shipowners Social Welfare Company SYN-ENOSIS Conflicts of interest statementThe authors have no conflict of interest related to this article

COMPARATIVE IMMUNOGENICITY OF BNT162b2 mRNA VACCINE WITH NATURAL COVID-19 INFECTION

The mRNA vaccine BNT162b2 has proven highly effective and currently many millions are being vaccinated. There are limited and conflicting data from immunogenicity studies on the effects of age, gender, vaccination side effects (VSE), risk factors for severe COVID-19 (RFS-COV), obesity (BMI) and previous SARS-CoV-2 (Pr-CoV) Moreover, immunogenicity data from COVID-19 patients comparing various disease categories of natural infection i.e. asymptomatic vs mild vs moderate vs severe infection are sparse, and include limited number of individuals. This study included 871 vaccinated health care workers (HCW) and 181 patients with natural infection. Immunogenicity was assessed by a quantative assay measuring anti-SARS-CoV-2 against the RBD domain of the spike protein (anti-RBD) and anti-SARS-CoV-2 against nucleocapsid protein (anti-N). Samples were collected 1-2 weeks after completion of the 2nd dose in the vaccinated HCWs and 15-59 days post symptoms onset in patients with natural infection. The concentration of anti-RBD in vaccinated individuals after multivariable analysis was significantly associated with age, gender, VSE and Pr-CoV. Specifically, anti-RBD median levels (95% CI) were lower by 2,466 (651-5,583), 6,228 (3,254-9,203) and 7,651 (4,479-10,823) AU/ml in 35-44, 45-54, 55-70 yrs respectively, compared with 18-34 yrs group. In females, median levels of anti-RBD were higher by 2,823 (859-4,787) compared with males, in individuals with VSE were higher by 5,024 (3,122-6,926) compared with no VSE, and in HCWs with Pr-CoV were higher by 9,971 (5,158-14,783) AU/ml compared with HCWs without Pr-CoV. Among individuals with natural infection, the median anti-RBD levels were 14.8 times higher in patients with critical COVID-19 infection compared with non-hospitalized individuals. The ratio of anti-RBD in vaccinated individuals versus those with natural infection varied from 1.0 up to 19.4 according to the clinical subgroup of natural infection. This study proves the high immunogenicity of BNT162b2 vaccine although its sustainability remains to be seen. The use of comparative data from natural infection serological panels, expressing the clinical heterogeneity of natural infection may facilitate early decisions for vaccine evaluation in clinical trials.

Evaluating the effects of vaccine rollout policies in European countries: A simulation study

The results of a simulation-based evaluation of several policies for vaccine rollout are reported, particularly focusing on the effects of delaying the second dose of two-dose vaccines. In the presence of limited vaccine supply, the specific policy choice is a pressing issue for several countries worldwide, and the adopted course of action will affect the extension or easing of non-pharmaceutical interventions in the next months. We employ a suitably generalised, age-structure, stochastic SEIR (Susceptible [->] Exposed [->] Infectious [->] Removed) epidemic model that can accommodate quantitative descriptions of the major effects resulting from distinct vaccination strategies. The different rates of social contacts among distinct age-groups (as well as some other model parameters) are informed by a recent survey conducted in Greece, but the conclusions are much more widely applicable. The results are summarised and evaluated in terms of the total number of deaths and infections as well as life years lost. The optimal strategy is found to be one based on fully vaccinating the elderly/at risk as quickly as possible, while extending the time-interval between the two vaccine doses to 12 weeks for all individuals below 75 years old, in agreement with epidemic theory which suggests targeting a combination of susceptibility and infectivity. This policy, which is similar to the approaches adopted in the UK and in Canada, is found to be effective in reducing deaths and life years lost in the period while vaccination is still being carried out.

Clinical features and outcomes of hospitalized COVID-19 patients in a low burden region.

Data on the clinical features and outcomes of COVID-19 patients from countries with low disease burden are rare. Greece, however, presented a low burden of COVID-19 disease during the first pandemic outbreak. This is a retrospective study of COVID-19 hospitalized patients in Greece. Clinical data were extracted from medical records using univariable and multivariable logistic regression analyses to assess the factors associated with Intensive Care Unit (ICU) admission and in-hospital death. Eighty-five patients were included in this study, 49 (57.7%) male with median (25th-75th) age 60 (49-72) years old. Sixty-one (72%) of them had at least one comorbidity with hypertension being the most common (45,6%). More than half (56%) had severe or critical disease, 20% required ICU care (14% received invasive ventilation) and 10.7% died. Solid tumor (p = 0.021) and NEWS score (p = 0.048), thrombocytopenia (p = 0.036) or involvement of all lung fields in chest x-ray (p = 0.002) on admission were independent risk factors for ICU admission. Immunosuppression (p = 0.032) and thrombocytopenia (p = 0.049) were independent predictors of death. Hospitalized COVID-19 patients in a European country with a low burden of the disease, in which hospital capacities had not been overwhelmed, had lower mortality rate compared to those reported for patients hospitalized in regions with a high burden of the disease.

Molecular epidemiology of SARS-CoV-2 in Greece reveals low rates of onward virus transmission after lifting of travel restrictions based on risk assessment during summer 2020

Molecular epidemiology has provided an additive value to traditional public health tools by identifying SARS-CoV-2 clusters, or providing evidence that clusters based on virus sequences and contact tracing are highly concordant. Our aim was to infer the levels of virus importation and to estimate the impact of public health measures related to travel restrictions to local transmission in Greece. Our phylogenetic and phylogeographic analyses included 389 SARS-CoV-2 sequences collected during the first 7 months of the pandemic in Greece and a random collection in 5 replicates of 3,000 sequences sampled globally, as well as the best hits to our dataset identified by BLAST. Phylogenetic analyses revealed the presence of 70 genetically distinct viruses identified as independent introductions into Greece. The proportion of imported strains was 41%, 11.5%, and 8.8% during the three periods of sampling, namely, March (no travel restrictions), April to June (strict travel restrictions), and July to September (lifting of travel restrictions based on a thorough risk assessment), respectively. These findings reveal low levels of onward transmission from imported cases during summer and underscore the importance of targeted public health measures that can increase the safety of international travel during a pandemic.

An improved method to estimate the effective reproduction number of the COVID-19 pandemic: lessons from its application in Greece

IntroductionMonitoring the time-varying effective reproduction number Rt is crucial for assessing the evolution of the COVID-19 pandemic. We present an improved method to estimate Rt and its application to routine surveillance data from Greece. MethodsOur method extends that of Cori et al (2013), adding Bayesian imputation of missing symptom onset dates, imputation of infection times using an external estimate of the incubation period, and an adjustment for reporting delay. To facilitate its use, we provide an R software package named "bayEStim". We applied the method to COVID-19 surveillance data from Greece, and examined the resulting Rt estimates in relation to control measures applied, in order to assess their effectiveness. We also associated Rt, as a measure of transmissibility, to population mobility as recorded in Google data and to ambient temperature. We used a serial interval between 4 and 7.5 days, and a median incubation period of 5.1 days. ResultsIn Greece Rt fell rapidly as the first control measures were introduced, dropping below 1 at least a week before a full lockdown came into effect. In mid-July Rt started increasing again, as increased mobility associated with tourism activity was observed. Each 10% of increase in relative mobility increased Rt by 8.1% (95% CrI 6.1-10.2%), whereas each unit celsius of temperature increase decreased Rt by 4.6% (95% CrI 5.4-13.7%). ConclusionsMobility patterns significantly affect Rt. Most of the reduction in COVID-19 transmissibility in Greece occurred already before the lockdown, likely as a result of decreased population mobility. Lower viral transmissibility in summer does not appear sufficient to counterbalance the increased mobility due to tourism. Monitoring Rt is an essential component of COVID-19 surveillance, and it is crucial for correctly assessing the effect of control measures.

Antibodies against SARS-CoV-2 among health care workers in a country with low burden of COVID-19

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 two hospitals and assess potential risk factors. Hospital-1 was involved in the care of COVID-19 patients while hospital-2 was not. A validated, rapid, IgM/IgG antibody point-of care test was used. 1,495 individuals consented to participate (response rate 77%). The anti-SARS-CoV-2 weighted prevalence was 1.07% (95%CI 0.37-1.78) overall and 0.44% (95%CI 0.12-1.13) and 2.4% (95%CI 0.51-8.19) in hospital-1 and hospital-2, respectively. The overall, hospital-1, and hospital-2 seroprevalence was 9, 3 and 20 times higher than the estimated infection attack rate in general population, respectively. Suboptimal use of personal protective equipment was noted in both hospitals. These data have implications for the preparedness of a second wave of COVID-19 epidemic.

Modelling the SARS-CoV-2 first epidemic wave in Greece: social contact patterns and impact assessment of social distancing interventions.

In Greece, a nationwide lockdown to mitigate the transmission of SARS-CoV-2 was imposed on March 23, 2020. As by the end of April the first epidemic wave is waning, it is important to assess the infection attack rate and quantify the impact of physical distancing. We implemented a survey to assess social mixing patterns before the epidemic and during lockdown. We estimated R0 from surveillance data and assessed its decline as a result of physical distancing based on social contacts data. We applied a Susceptible-Exposed-Infectious-Recovered model to estimate the infection attack rate and the infection fatality ratio (IFR). As multiple social distancing measures were implemented simultaneously (schools/work/leisure), we assessed their overall impact as well as their relative contribution. R0 was estimated 2{middle dot}38 (95%CI: 2{middle dot}01,2{middle dot}80). By April 26th, the infection attack rate was 0{middle dot}12% (95%CrI: 0{middle dot}06%,0{middle dot}26%) and the IFR 1{middle dot}12% (95%CrI: 0{middle dot}55%,2{middle dot}31%). During lockdown, daily contacts were reduced by 86{middle dot}9% and the effective reproduction number reached 0{middle dot}46 (95%CrI: 0{middle dot}35,0{middle dot}57). The reduction in R0 attributed to lockdown was 81{middle dot}0% (95%CrI: 71{middle dot}8%,86{middle dot}0%) whereas the reduction attributed to each measure separately ranged between 10%-24%. We assessed scenarios with less disruptive social distancing measures as well as scenarios where measures are partially lifted after lockdown. This is the first impact assessment of the first wave of SARS-CoV-2 in a European country. It suggests that only multiple measures implemented simultaneously could reduce R0 below 1. Measuring social mixing patterns can be a tool for real-time monitoring of the epidemic potential.