Immune response to SARS-CoV-2 in health care workers following a COVID-19 outbreak: A prospective longitudinal study

Abstract

Objective Currently, little is known about the progression of an immune response against SARSCoV- 2 upon infection or sub-infection-exposure over time. We examined the serologic response in healthcare workers up to 12 weeks after a well-documented and contained outbreak and compared results with findings from earlier serologic testing in the same population. Methods This study followed 166 health care workers of the University Perinatal Care Center, Regensburg, Germany, for up to 12 weeks. 27 of the subjects had previously tested positive for the presence of SARS-CoV-2 by PCR testing and developed COVID-19. Serologic responses were tested with two independent commercially available test kits. Results 77.8 % of COVID-19 study subjects developed a specific IgG-response over the course of the 12-week study, while none of the COVID-19 contact groups had a detectable IgG response. Amongst most COVID-19 patients the values of detectable IgG-responses significantly increased over time as confirmed with both tests, while that of positive IgA responses decreased. Between the number of reported symptoms and antibody responses in COVID-19 patients no correlation was found and no new cases of seroconversion were identified in asymptomatic coworkers with negative PCR during the outbreak. Conclusions Immune response after COVID-19 increases significantly over time but still approximately 22 % of COVID-19 patients did not mount a measurable serologic immune response within 60 days. Exposed co-workers did not develop any relevant antibody levels at all. We conclude that immunity after infection increases over time, but the antibody response does not develop reliably in all infected people.

SARS-CoV-2 induces a durable and antigen specific humoral immunity after asymptomatic to mild COVID-19 infection

“…We furthermore corroborate prior findings of strong concordance between SARS-CoV-2 anti-spike IgG and virus neutralization capacity, supporting a longlasting and durable immunity after COVID-19 infection also in individuals with no or mild symptoms. Anti-nucleocapsid IgG, however, declined in individuals with asymptomatic to mild COVID-19 disease, implying that this antigen may not be a useful target in long-term serological population studies.Our findings of a durable IgG response are consistent with recent studies showing stable antibody levels for up to 2-6 months(16)(17)(18)(19). Several other studies, however, report a rapid decline in circulating SARS-CoV-2 antibodies (10-12), especially after mild disease(13)(14)(15).Since the onset of the COVID-19 pandemic a plethora of serological assays have emerged, using different methods such as ELISA, CLIA, lateral flow and multiplex systems(23).Although the discrepancies regarding the longevity of SARS-CoV-2 antibodies may well stem from variations in sensitivity and specificity of these assays, the target antigen of choice is a likely contributing factor.…”

“…The kinetics, duration and efficacy of circulating SARS-CoV-2 antibodies are however, due to the novelty of the virus, less established. In fact, conflicting studies provide data on a rapid decline in circulating IgG antibodies within weeks after COVID-19 (10)(11)(12), especially after mild disease (13)(14)(15), while others report detectable antibodies up to two to six months after symptom onset (16)(17)(18)(19).…”

SARS-CoV-2 seroconversion among 4040 Egyptian healthcare workers in 12 resource-limited healthcare facilities: A prospective cohort study

“…A weak or even lack of seroconversion after initial PCR positivity was reported among some COVID-19 patients during variable periods of follow-up, leaving these individuals susceptible to infection or relapse ( Papachristodoulou et al 2020 ). For example, 22% of 27 patients did not develop a serologic response after 60 days of follow-up in Germany; ( Fill Malfertheiner et al, 2020 ) 20% of 173 Chinese patients did not develop IgG after two weeks of onset; ( Zhao et al, 2020 ) 6% did not show any antibody response two weeks after hospital discharge and 30% of 175 patients showed very low neutralizing antibody titres in Shanghai, China; ( Wu et al, 2020 ) and one of 14 (7%) HCWs had not seroconverted after 17 days of follow-up in the UK. ( Houlihan et al, 2020 ) Among this Egyptian HCW cohort, 66.7% of 45 seronegative HCWs who tested PCR-positive only at baseline did not seroconvert after three weeks of follow-up.…”

COVID-19 Antibody Tests and Their Limitations

“… 61 However, some infected individuals did not seroconvert or their antibody titers waned within short periods of time following initial production. 117 , 161 , 162 , 198 , 199 …”