Berselli N, Filippini T, Paduano S, Malavolti M, Modenese A, Gobba F, Borella P, Marchesi I, Vivoli R, Perlini P, Rossana Bellucci R, Bargellini A, Vinceti M
2nd edition of “Le giornate della ricerca scientifica e delle esperienze professionali dei giovani”, December 17-18, 2020. Webinar
Abstract
Introduction: The spread of the COVID-19 outbreak, due to infection from SARS-CoV-2, occurred all around the world in the spring of 2020, with extremely severe consequences in terms of hospitalizations and deaths. In Italy the epidemic was first recognized on 21 February 2020. There was a first wave that mainly affected Northern Italy, with a rapid rise in the number of cases and a peak on 21 March, followed by a decline and stabilization of cases in June and July. Italy is currently witnessing a second wave of the outbreak throughout its entire territory. In the present study, we investigated serum anti-SARS-CoV-2 antibody prevalence between 1 June and 25 September 2020 in 7,561 subjects in Modena, Northern Italy.
Methods:
We investigated 5,454 workers, who participated to testing campaign offered by their companies, and 2,107 residents who independently decided to undergo the examination at the Test Laboratory in Modena. Upon approval by the local Ethics Committee, we analyzed the results of this analytical campaign, and specifically of serological tests to detect serum anti-SARS-CoV-2 antibody in the subjects tested from 1 June to 25 September 2020. We considered both quantitative and qualitative tests carried out on these samples. We computed absolute and relative prevalence of serum antibodies against SARS-CoV-2 in the whole study population and in selected subgroups. To consider the subjects based on the professional class to which they belong, we used the categories in the 2007 ATECO classification of economic activity.
Results: The overall seroprevalence was 4.7%, higher in females (5.4%) than in males (4.3%), and in the oldest age groups (7.3% between 60 and 69 years, and 11.8% ≥70 years). Furthermore, seroprevalence proved higher in subjects tested with the quantitative test (5.8%) compared to the rapid qualitative one (2%). Among the occupational categories, we found the highest seroprevalence in healthcare workers (8.8%), dealers and vehicle repairers (5.2%) and workers in the sports sector (4.0%). Seroprevalence was lower for office workers (3.3%), people working in water supply and waste management sector (2.4%) and manifacturers (2.0%), and even lower or null for those employed in sectors such as transport and storage, accommodation and restaurant services, and the school system.
Conclusions: The higher seroprevalence in females may indicate a greater susceptibility to infection, a lower COVID-19 lethality compared to males, or an effect of the familial, social and occupational roles of women, leading to an increased risk of contracting the virus. The steep increase in seroprevalence in the older age groups, together with the higher mortality affecting them, is of paramount relevance for the evaluation of specific protection policies for these subjects at high risk. Considering occupational risk factors, and not unexpectedly, seroprevalence was higher in healthcare workers, most exposed to SARS-CoV-2 infection, followed by dealers, vehicle repairers and sportsmen. The results in healthcare operators are in agreement with data previously observed in other studies and may underline the high risk of infection experienced by this crucial sector and the need to increase their protective measures for these workers. We found that workers heavily involved in routine contacts with different people (clients, patients, sports opponents) had a higher seroprevalence of anti-SARS-CoV-2 antibodies. On the other hand, no excess seropositivity emerged for office workers having no contact with the public as expected, for manufacturing and construction workers, and for employees in transportation and storage. This indicates that, so far, these sectors have enforced adequate physical distancing and use of personal protective equipment to mitigate the risk of SARS-CoV-2 infection. The absence of increased risk for workers in the education sector was probably strongly favored by the limited mobility and smart working of employees during the national lockdown. Interestingly, the subgroup “production of meat products” did not show any positivity to the serological test, contrary to what expected given the occurrence of small outbreaks in slaughterhouses in other regions.
In conclusion, we have assessed in detail the seroprevalence of anti-SARS-CoV-2 antibodies in an Italian area severely hit by the first wave of Covid-19, the Emilia-Romagna region. This will also allow to estimate Covid-19 infection fatality ratio, while the only estimate available so far in this area has been case-fatality ratio.