Seroprevalence of anti-SARS-CoV-2 IgG among healthcare workers of a large university hospital in Milan, Lombardy, Italy: a cross-sectional study

Abstract

ObjectivesTo assess the seroprevalence of anti-SARS-CoV-2 IgG among health careworkers (HCWs) in our university hospital and verify the risk of acquiring the infection according to work area.DesignCross-sectional study.SettingMonocentric, Italian, third-level university hospital.ParticipantsAll the employees of the hospital on a voluntary base, for a total of 4055 participants among 4572 HCWs (88.7%).Primary and secondary outcome measuresNumber of anti-SARS-CoV-2 positive serology according to working area. Association of anti-SARS-CoV-2 positive serology to selected variables (age, gender, country of origin, body mass index, smoking, symptoms and contact with confirmed cases).ResultsFrom 27 April 2020 to 12 June 2020, 4055 HCWs were tested and 309 (7.6%) had a serological positive test. No relevant difference was found between men and women (8.3% vs 7.3%, p=0.3), whereas a higher prevalence was observed among foreign-born workers (27/186, 14.5%, p<0.001), employees younger than 30 (64/668, 9.6%, p=0.02) or older than 60 years (38/383, 9.9%, p=0.02) and among healthcare assistants (40/320, 12.5%, p=0.06). Working as frontline HCWs was not associated with an increased frequency of positive serology (p=0.42). A positive association was found with presence and number of symptoms (p<0.001). The symptoms most frequently associated with a positive serology were taste and smell alterations (OR 4.62, 95% CI: 2.99 to 7.15) and fever (OR 4.37, 95% CI: 3.11 to 6.13). No symptoms were reported in 84/309 (27.2%) HCWs with positive IgG levels. Declared exposure to a suspected/confirmed case was more frequently associated (p<0.001) with positive serology when the contact was a family member (19/94, 20.2%) than a patient or colleague (78/888, 8.8%).ConclusionsSARS-CoV-2 infection occurred undetected in a large fraction of HCWs and it was not associated with working in COVID-19 frontline areas. Beyond the hospital setting, exposure within the community represents an additional source of infection for HCWs.

SARS-CoV-2 anti-spike antibody titres after vaccination with BNT162b2 in naïve and previously infected individuals

“…Regarding the highest titres observed among those who presented symptoms, this parallel similar observations that our and other groups have made also for anti-N antibodies, elicited only by natural infection [ 10 ]. Among the other, Legros et al demonstrated how neutralizing antibodies (nAb) titres correlated strongly with disease severity and with anti-spike IgG levels, with patients from intensive care units exhibiting high nAb titres whereas asymptomatic or exclusive outpatient-care patients had no or low nAbs [ 11 ].…”

“…Interestingly, as we previously observed for anti-N antibodies, anti-S1 antibodies titres were lower among smokers [ 10 ]. This confirm the impact of smoking on the immune system and its ability to mount an humoral response to inhaled but also injected antigens, a finding in contrast with previous evidence which suggested an influence only on inhaled antigens [ 12 ].…”

ANTI - SARS-CoV-2 ANTIBODY SCREENING IN HEALTH CARE WORKERS AND ITS CORRELATION WITH CLINICAL PRESENTATION

“…in Spain have discussed ageusia and anosmia as the most predictive symptoms of COVID-19 infection in their studies (13, 16). Our study showed lower percentage of seropositive HCWs showing anosmia and ageusia which could be described as variation due to subjects characteristics and geographical variations(14). We found that 34.1% of seropositive HCWs were asymptomatic until the time of investigation since the last 6 months.…”

“…Similar study performed by Lombardi Andrea et.al. in Italy revealed the Seroprevalence rate to be 7.6% (14). The higher seroprevalence in our study is corresponding with the 24.4% prevalence rate as reported by Adrian M. et.al.…”

“…in Geneva had shown that the antibody titers donot reduce until 6 months after the infection (18). Studies around the globe like study in Italy (14), study in Spain(16), Study in UK (15) have shown the significant associataion between the positive serology and the presence of symptoms. Body ache and headache were the most common symptoms followed by fever and dry cough among the seropositive HCWs in this study.…”