Antibody Status and SARS-CoV-2 Infection in Health Care Workers

Feb 11, 2021
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Authors:
Lumley SF, O'Donnell D, Stoesser NE, et al., on behalf of the Oxford University Hospitals Staff Testing Group.
Citation:
Antibody Status and Incidence of SARS-CoV-2 Infection in Health Care Workers. N Engl J Med 2021;384:533-540.
Summary By:
Debabrata Mukherjee, MD, FACC

Quick Takes

  • The presence of anti-spike antibodies is associated with a substantially reduced risk of PCR-confirmed SARS-CoV-2 infection over 31 weeks of follow-up.
  • Overall, these data suggest that SARS-CoV-2 infection provides some immunity against reinfection.
  • Longer-term follow-up beyond 6 months is indicated to assess durability and degree of protection for reinfection.

Study Questions:

What is the relative incidence of subsequent positive severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) polymerase chain reaction (PCR) tests and symptomatic infections in health care workers who were seropositive for SARS-CoV-2 antibodies?

Methods:

The authors investigated the incidence of SARS-CoV-2 infection confirmed by PCR in seropositive and seronegative health care workers attending testing of asymptomatic and symptomatic staff at Oxford University Hospitals in the United Kingdom. Baseline antibody status was determined by anti-spike (primary analysis) and anti-nucleocapsid IgG assays, and staff members were followed for up to 31 weeks. The authors used Poisson regression to model the incidence of PCR-positive infection per at-risk day according to baseline antibody status, adjusting for incidence over time, age, and participant-reported gender.

Results:

A total of 12,541 health care workers participated and had anti-spike IgG measured; 11,364 were followed up after negative antibody results and 1,265 after positive results, including 88 in whom seroconversion occurred during follow-up. A total of 223 anti-spike–seronegative health care workers had a positive PCR test (1.09 per 10,000 days at risk), 100 during screening while they were asymptomatic and 123 while symptomatic, whereas two anti-spike–seropositive health care workers had a positive PCR test (0.13 per 10,000 days at risk), and both workers were asymptomatic when tested (adjusted incidence rate ratio, 0.11; 95% confidence interval, 0.03-0.44; p = 0.002). There were no symptomatic infections in workers with anti-spike antibodies. Rate ratios were similar when the anti-nucleocapsid IgG assay was used alone or in combination with the anti-spike IgG assay to determine baseline status.

Conclusions:

The authors concluded that presence of anti-spike or anti-nucleocapsid IgG antibodies was associated with a substantially reduced risk of SARS-CoV-2 reinfection in the ensuing 6 months.

Perspective:

This longitudinal cohort study reports that the presence of anti-spike antibodies was associated with a substantially reduced risk of PCR-confirmed SARS-CoV-2 infection over 31 weeks of follow-up. These data suggest that previous infection resulting in antibodies to SARS-CoV-2 is associated with protection from reinfection for most people for at least 6 months. Overall, these data suggest that SARS-CoV-2 infection provides some immunity against reinfection. Longer-term follow-up beyond 6 months is indicated to assess durability and degree of protection.

Clinical Topics: COVID-19 Hub, Prevention

Keywords: Antibodies, Coronavirus, COVID-19, Health Personnel, Hospitals, University, Immunity, Immunoglobulin G, Nucleocapsid, Polymerase Chain Reaction, Primary Prevention, severe acute respiratory syndrome coronavirus 2


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