key: cord-0302769-4266liiw
authors: Adorni, F.; Jesuthasan, N.; Perdixi, E.; Sojic, A.; Giacomelli, A.; Noale, M.; Trevisan, C.; Franchini, M.; Pieroni, S.; Cori, L.; Mastroianni, C. M.; Bianchi, F.; Antonelli Incalzi, R.; Maggi, S.; Galli, M.; Prinelli, F.
title: Epidemiology of SARS-CoV-2 infection in Italy using real-world data: methodology and cohort description of the second phase of web-based EPICOVID19 study.
date: 2022-01-10
journal: nan
DOI: 10.1101/2022.01.10.22268897
sha: 5c628a7c9ffeb6e0b4500fd48d2fbb5002225654
doc_id: 302769
cord_uid: 4266liiw

Digital technologies have been extensively employed in response to the SARS-CoV-2 pandemic worldwide. This study describes the methodology of the two-phase internet-based EPICOVID19 survey, and the characteristics of the adult volunteers respondents who lived in Italy during the first (April - May 2020) and the second wave (January - February 2021) of the epidemic. Validated scales and ad-hoc questionnaires were used to collect socio-demographic, medical and behavioural characteristics, as well as information on COVID-19. Among those who provided email addresses during phase I (105,355), 41,473 participated in phase II (mean age 50.7 years +/- 13.5 SD, 60.6% females). After a median follow-up of ten months, 52.8% had undergone naso-pharyngeal swab (NPS) testing and 13.2% had positive result. More than 40% had undergone serological test (ST) and 11.9% were positive. Out of the 2,073 participants with at least one positive ST, 72.8% had only negative results from NPS or never performed it. These results indicate that a large fraction of individuals remained undiagnosed, possibly contributing to the spread of the virus in the community. Participatory online surveys offer a unique opportunity to collect relevant data at individual level from large samples during confinement.

The coronavirus disease caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), has posed an unprecedented public health emergency worldwide [1] . As of December 20, 2021, with 5,389,155 confirmed cases and 135,641 deaths Italy was the first Western country to be severely affected by the COVID-19 pandemic [2] .

During the first wave of the pandemic peak worldwide, epidemiological surveillance strategies were mainly based on the testing of symptomatic patients with serious diseases requiring hospitalization and intensive medical care [3, 4] . Despite efforts to ensure universal access to molecular testing, the massive spread of the infection has de facto restricted the diagnosis of COVID-19 to the fraction of infected people who exhibited severe symptoms only. This limitation, combined with the lack of official standards in the detection and diagnosis of asymptomatic or pauci-symptomatic patients, heavily affected the effectiveness of testing strategies and contact tracing, which in turn compromised the control of the spread of SARS-CoV-2 in the community [5] . As result of the limited availability of population-based data, the inconsistency between official statistics of different countries has made a global comparison difficult [6] .

To easily and freely collect real-time and population-based data, multiple eHealth technologies have been employed [7] . In several countries, such as the UK [8] , US [9] , Israel [10] , and Canada [11, 12] , large numbers of participants were recruited via mobile applications and web-based tools, to collect information on symptoms, psychosocial determinants, behavioural changes, to monitor positive cases and in some circumstances to carry out contact tracing. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint

The copyright holder for this this version posted January 10, 2022. ; https://doi.org/10.1101/2022.01. 10 .22268897 doi: medRxiv preprint anosmia, dysgeusia, fever, shortness of breath, and cough were consistently observed in association with the self-reported positive SARS-CoV-2 test, highlighting the relevance of collaborative syndromic surveillance during pandemic waves worldwide [13] . Furthermore, digital epidemiological surveillance has filled in the gaps due to the lack of seroprevalence studies, attempting to size up more completely the real, yet unknown, spread of the epidemic.

In response to the COVID-19 pandemic and to the lack of Italian epidemiological data on persons who experienced the mild-to-severe disease in the general population, a large sample of more than 198,000 voluntary adults who lived in Italy during the first lockdown was recruited through a web-based approach. These data allowed to better understand the association of symptoms (or cluster of symptoms) [14] [15] [16] and smoking habits [17] with COVID-19, the role of vaccination for other vaccine-preventable diseases [18, 19] , as well as to characterize psychological aspects of the population [20] and health policy issues [21] in the context of the pandemic. During the second wave of the epidemic in Italy, a follow-up questionnaire was sent by e-mail to collect further data on SARS-CoV-2 testing, COVID-19 related symptoms, hospitalization, and behavioural and psychosocial factors associated with the pandemic. This article describes the rationale, methodology, and sociodemographic and clinical characteristics of people who participated in the second phase of the internet-based EPICOVID19 study in Italy, in January-February 2021.

EPICOVID19 is an Italian national internet-based survey with a cross-sectional research design in phase I [14] and a longitudinal design in phase II, carried out on a self-selected sample of adult volunteers (18+ years old) living in Italy during the first and second waves of the pandemic. The EPICOVID19 study was established as a collaborative project of a . CC-BY-NC-ND 4.0 International license It is made available under a perpetuity.

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The copyright holder for this this version posted January 10, 2022. ; https://doi.org/10.1101/2022.01.10.22268897 doi: medRxiv preprint working group including epidemiologists, physicians with expertise in infectious diseases, biostatisticians and public health professionals, with the aim of improving knowledge about SARS-CoV-2 infection. The EPICOVID19 survey was designed after a comprehensive literature review of existing research as to ensure maximal harmonisation and comparability with other large population studies. Most of the items in the questionnaire were chosen based on standardized, validated scales. The working group tested both questionnaires for two weeks and then edited them according to the feedback before launching them in the general population.

Participants were asked to complete the two questionnaires (phase I and II) after reading an introductory page (which briefly described the rationale and objectives of the study and the scientific consortium), and after accepting the option to provide consent to participate. The content of the first questionnaire was previously described in detail [14] . The phase II questionnaire is reported as Annex 1, and a comparison of its content with the one of phase I is presented in Table S1 . The validated scales and questionnaires used in the two surveys are described as Table S2 .

The two-wave web-based surveys were implemented using the European Commission's official open-source management tool EUSurvey (https://ec.europa.eu/eusurvey). The link to the first questionnaire was shared since 13 th April to 2 nd June 2020, when the Italian government was applying the strictest lockdown on the entire population. Participation was asked through mailing lists, social media platforms (Facebook, Twitter, Instagram, WhatsApp), press releases, internet pages, television and radio news programs, word of mouth and the study website (https://epicovid19.itb.cnr.it/). Inclusion criteria were age ≥18 . CC-BY-NC-ND 4.0 International license It is made available under a perpetuity.

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The copyright holder for this this version posted January 10, 2022. ; https://doi.org/10.1101/2022.01.10.22268897 doi: medRxiv preprint years, access to a mobile phone, computer or tablet with internet connectivity and provision of online consent to participate in the study. In total, 207,341 participants clicked on the first questionnaire link and 198,822 provided consent to participate and completed the first online survey. Participants who had consented to be contacted (N=105,355, 53%), by providing their personal email address during the first survey, received an email invitation (since January 15 to February 28, 2021) containing a personalised link that allowed them to complete the second questionnaire. In that period the restrictions in Italy were less severe than during the first phase of the survey. Those who had not completed the EPICOVID19 phase II questionnaire within fifteen days since invitation received up to three reminder emails. Exclusion of participants who did not receive the invitation or did not respond (N=63,203), who did not provide consent (N=653), and of those with inconsistencies in email contacts or who answered more than once using the same email address (N=26) resulted in 41,473 respondents included in the present analysis ( Figure 1 ). is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint

The copyright holder for this this version posted January 10, 2022. ; https://doi.org/10.1101/2022.01.10.22268897 doi: medRxiv preprint Excluded participants (N=157,349) were younger, more likely residents in Southern regions or islands, with a lower educational level and more frequently students (Table S3 ).

Variables of interest for the present study were the following: socio-demographic information (age, education, employment, job position at-risk for the infection, socio-economic status), body mass index (BMI, calculated as weight divided by height squared), number of chronic diseases, smoking habit, alcohol consumption, self-perceived health status [22] recoded as bad or very bad, adequate, and good or very good. Townsend Deprivation Scores (TDSs) was calculated as proxy for individual level deprivation [23] by summing up, for each participant, the following variables (both dichotomized): unemployment, non-ownership of the house where he/she lives, no car owned by family members, and house crowding (defined as number of cohabitants greater than the number of rooms in the house, kitchen and bathrooms excluded). The total score ranged 0 to 4, with higher score indicating higher deprivation. Sleep problems were measured using the Jeskin Sleep Scale (JSS) [24] based on four items. Each one was rated on a Likert-like scale from 0 to 5, and the total score was the sum of all four items' scores and ranged from 0 (no sleep problems) to 20. The continuous score was dichotomized as follows: score lower than 11 showing low frequency of sleep disturbances and score greater than 10 indicating high frequency of sleep disturbances) [25] . Personal stress was measured using the 10-item Perceived Stress Scale (PSS) [26] and adding five items developed ad-hoc. Each item was rated on a Likert-like is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint

The copyright holder for this this version posted January 10, 2022. ; https://doi.org/10.1101/2022.01.10.22268897 doi: medRxiv preprint economic and job situation, and fear about the relatives' economic and job situation were assessed with a short questionnaire developed ad-hoc for the present survey. Each aspect was rated on a Likert-like scale from 0 (no fear) to 4, and the total score was the sum of all four items' scores and ranged from 0 to 16, with higher scores indicating higher fear. 

The continuous variables were represented as mean and standard deviation (SD) and the categorical variables were expressed as numbers and percentages. The Student t-test and chi-square test were used to compare the respondents' characteristics by sex for continuous and categorical variables, respectively. The threshold of statistical significance for any test was set at P-values of 0.05. All of the statistical analyses were carried out using STATA 

The Ethics Committee of the Istituto Nazionale per le Malattie Infettive IRCCS Lazzaro Spallanzani approved the EPICOVID19 first (protocol No. 70, 12/4/2020) and second phase . CC-BY-NC-ND 4.0 International license It is made available under a perpetuity.

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The copyright holder for this this version posted January 10, 2022. ; https://doi.org/10.1101/2022.01.10.22268897 doi: medRxiv preprint (protocol No. 249, 14/1/2021) study protocols. When participants first accessed the webbased platform, they were informed about the study and its purpose, the data to be collected, and the methods of storage; they then filled in the informed consent form. Participants were able to start the EPICOVID19 questionnaire only after consenting. Participation was voluntary and no compensation was given to respondents. The planning, conduct, and reporting of the study were in line with the Declaration of Helsinki, as revised in 2013. Data were handled and stored following the European Union General Data Protection Regulation (EU-GDPR) 2016/679, and housed in the ITB-CNR server in Italy. Data transfer was safeguarded by encrypting and decrypting data and password protection. Study design and data were registered in ClinicalTrials.gov, NCT04471701.

The results of the first phase of the EPICOVID19 web-based survey were communicated mainly through peer-reviewed publications [14] [15] [16] [17] [18] [19] [20] [21] in international scientific journals, meetings and conference presentations, workshops, the study website (www.epicovid19.itb.cnr.it); and disseminated through audio and video interviews and local printed media. A personalized e-mail with the provision of the results was sent to each participant who completed the survey and accepted to be contacted for communications about the project.

The standardized response rates per 100,000 inhabitants by Italian regions over the January-February 2021 study period are represented in Figure 2 and Table S4 . The percentages relating to the regional distribution of the Italian population were taken from the ISTAT website [27] . The darkest colour means the highest response rate, which was higher in the northern regions (Lombardia 137.5, Piemonte 106.6, Emilia-Romagna 100.6).

. CC-BY-NC-ND 4.0 International license It is made available under a perpetuity.

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The copyright holder for this this version posted January 10, 2022. ; https://doi.org/10.1101/2022.01.10.22268897 doi: medRxiv preprint is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint

The copyright holder for this this version posted January 10, 2022. . CC-BY-NC-ND 4.0 International license It is made available under a perpetuity.

is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint

The copyright holder for this this version posted January 10, 2022. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint

The copyright holder for this this version posted January 10, 2022. ; https://doi.org/10.1101/2022.01.10.22268897 doi: medRxiv preprint molecular NPS testing and among them 2,902 (13.2%) tested positive at least once, with no differences between males (13.7%) and females (13.0%). is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint

The copyright holder for this this version posted January 10, 2022. The three most frequent self-referred symptoms ( Figure 3 , is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint

The copyright holder for this this version posted January 10, 2022. ; https://doi.org/10.1101/2022.01.10.22268897 doi: medRxiv preprint 

This is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint

The copyright holder for this this version posted January 10, 2022. ; https://doi.org/10.1101/2022.01.10.22268897 doi: medRxiv preprint and the frequency of COVID-19 related symptoms in a median study period of eleven months since March 2020.

The EPICOVID19 questionnaires had the power to collect some data useful to characterize the individual behaviours of the respondents involving several aspects of daily life usually not collected in clinical context. The national coverage of the survey was in line with the geographical spread of COVID-19 during the first wave [2] , when participants were recruited.

As to work conditions, the majority of the participants (63%) maintained their stable work position with the 18% shifting to work from home, data quite in accordance with the Eurostat Statistics. In 2020, 12.3% of employed aged 15-64 years said they often work in agile mode in the European Union, and an identical percentage was reported in Italy (12.2%) [28] .

Furthermore, according to the Smart Working Observatory of the Politecnico di Milano [29] , during the lockdown about 6.6 million workers shifted to remote working. Among the work category at high risk of infection, school staff and healthcare workers represent almost 30% of the study sample, with a significant unbalance toward the female sex, as expected.

Regarding the perception of health status and mood disorders, 78.7% referred to perceive a good or very good health status with no substantial difference between females and males.

However, 8.1% and 50.0% reported sleep disorders and moderate-to-high self-perceived stress during the month before the survey completion, respectively. Similarly to these findings, recent studies reported a high prevalence of sleep problems [30] and a high level of stress or anxiety [31] during the COVID-19 outbreak. The results of the present study also showed that females are more likely to manifest sleep disorders and psychological stress as pointed out in other investigations [32, 33] . Furthermore, females are more worried about contagion for themselves or relatives and about personal and relatives' economic and job situation, confirming the results of phase I of the EPICOVID19 survey [20] . These data reinforce indications that although males are at higher risk of developing a severe infection is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint

The copyright holder for this this version posted January 10, 2022. ; https://doi.org/10.1101/2022.01.10.22268897 doi: medRxiv preprint than females [34] , the latter are more concerned about COVID-19. This could reflect a stronger adherence to virtuous behaviours in females compared to males [35] .

Considering the COVID-19-related variables, during the second survey, fever, headache myalgia, and olfactory and taste disorders were the most frequent self-reported symptoms among those who tested positive, which are consistently reported as peculiar symptoms associated with SARS-CoV-2 infection [13, 14, 36] . More than half of the sample underwent the NPS test (positive rate of 13.2%), because of suspected symptoms or contact with a COVID-19 case. More than 40% referred to having shared the workplace in the two weeks before having been tested. About 40% of the sample performed a ST, mostly voluntarily, and 11.9% resulted positive. Taken together, these percentages are significantly higher compared to the official number of positive cases officially reported in Italy for the period March 2020 -February 2021 (N=2.925.265 cases in 59.641.488 residents) [2, 27] , confirming the potential large underestimation of the actual number of exposed or infected.

Ideally, only by combining large seroprevalence epidemiological studies (screening tool) with massive NPS testing (diagnostic tool) this issue could be addressed. Most recent Italian serosurveillances still report a very broad range of prevalence estimates. Vena et al. [37] reported 11% IgG and/or IgM positivity in a large adult Italian population between March and April 2020. Among the volunteers recruited in the Marche region from March to June 2020, the authors found a seroprevalence of 14.4%, without significant differences between sex and age groups [38] . As of June 2020, in a population-based study [39] carried out in a northern municipality that was heavily affected by SARS-CoV-2 infection, authors found an overall positivity to SARS-CoV-2 of 22.6%, varying according to age groups. On the other side, the Italian National Institute of Statistics (ISTAT) estimated a much lower seroprevalence of 2.5% in a large sample from 2,000 Italian municipalities during the summer of 2020 [40] . Looking at other countries, a systematic review and meta-analysis that included 47 studies involving 399,265 people from 23 countries up to 14th August 2020, is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint

The copyright holder for this this version posted January 10, 2022. ; https://doi.org/10.1101/2022.01.10.22268897 doi: medRxiv preprint reported a seroprevalence that varied from 0.37% to 22.1% in the general population.

Limiting the analysis to the Italian dataset, the authors reported a pooled seroprevalence of 7.27 (95%CI 2. 48-11.9 ) and an estimated number of people infected by SARS-CoV-2 of 4,395,587 (95%CI 1,499,457-7,249,393) [41] .

Our large-scale data showed no sex difference in the proportion of respondents infected with SARS-CoV-2, in accordance with current knowledge. Although epidemiological evidence in the early phase of pandemic suggested that males had higher risk of SARS-CoV-2 infection than females [42] , subsequent evidence demonstrated that this risk difference was not significant [43] . This indicates that unequal access to healthcare and testing between sexes could have skewed towards a male bias in diagnosing the infection during the first wave of the pandemic. On the other hand, males were more frequently hospitalized and possibly manifested a more severe disease than females in the present sample. This is consistent with the large body of literature reporting that males face higher rates of hospitalization, intensive therapy unit admission and death compared to females [34] . We also observed specific sex-differences in relation to the self-reported COVID-19like symptoms, in which females tend to systematically over-report symptoms. Because no sex difference in the rate of positivity to the diagnostic or screening test has been observed, a possible explanation might reside in the fact that females were more worried about the health situation and tended to be more prone to the phenomenon of the 'nocebo effects' compared to males, as shown in other studies [44] [45] [46] . In line with available evidence, considering only participants with positive results from NPS and/or ST, males more often reported symptoms, such as fever and cough, known as predictors of worse outcomes [47] whereas females reported more frequently symptoms susceptible to subjective perception (headache, anosmia, dysgeusia, sore throat) and generally associated with less severe infections [48, 49] . is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint

The copyright holder for this this version posted January 10, 2022. [5] . Consequently, the number of SARS-CoV-2 infections in the asymptomatic or subclinical infected individuals was largely undetected [53] thus leading to a considerable underestimation of the number of actual cases [54, 55] .

This large fraction of people, not undergone self-isolation or quarantine, is likely to have is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint

The copyright holder for this this version posted January 10, 2022. ; https://doi.org/10.1101/2022.01.10.22268897 doi: medRxiv preprint outbreaks in small communities such as households [56] during the most severe restrictions period, or such as workplaces [57] , when the restrictions were less stringent.

The full body of results presented in this descriptive manuscript highlights a number of interesting topics that we will address in detail and with specific methodologies and approaches in future publications.

The present study has some weaknesses, primarily because the online system and voluntary participation suffers from inherent selection bias and generalizability. Similarly to other web-based survey [8, 58, 59] , some of the characteristics of the sample were not adequately representative of the Italian adult population. Indeed, females, younger, healthier and wealthier people were proportionally more represented in the enrolled sample than in the general population. Furthermore, data were self-reported, which might have introduced measurement and recall bias (e.g. survey question misunderstanding, etc.). In addition, the longitudinal design may have led to bias due to the loss of participants during the follow-up period. The response rate to the second survey was 40%, with some differences between included and excluded participants, in particular regarding age, education, employment status and geographical area of residence.

The present study also has several strengths including its community-based longitudinal design with two-time point's measures overlapping with the first and second wave of the epidemic in Italy, thus providing reliable details on the temporal evolution of the symptoms and testing. In addition, although these data were self-reported, almost 50% of the studied sample underwent a NPS or ST, providing an overarching picture of the positivity rate at the population level in a country in which the ability to track COVID-19 cases in real-time was limited. The exhaustive data collection on socio-demographic, medical, behavioural, and psychological factors, as well as the large sample size, is a further strength of this study. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint

The copyright holder for this this version posted January 10, 2022. ; https://doi.org/10.1101/2022.01.10.22268897 doi: medRxiv preprint Finally the EPICOVID19 web survey has reached a large sample of adults covering all Italian regions, although the response rate was unbalanced in favour of the northern regions, being the Italian geographical area more dramatically affected by the first wave of the pandemic at the time of enrolment. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint

The copyright holder for this this version posted January 10, 2022. 

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Aggregated data and the analysis source code will be made available on reasonable request to the corresponding author.

The authors declare no conflict of interest. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint

The copyright holder for this this version posted January 10, 2022. ; https://doi.org/10.1101/2022.01.10.22268897 doi: medRxiv preprint

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The authors would like to thank all the participants who took part in this study and made it possible, and all the collaborators of the EPICOVID19 Working Group