BACKGROUND AND PURPOSE:

• Lumley et al. (NEJM, 2020) assessed the incidence of positive SARS-CoV-2 tests and symptomatic COVID-19 infections in health care workers who were seropositive for SARS-CoV-2 antibodies

METHODS:

• Cohort study
• Setting
  • Oxford University Hospitals in the UK
• Participants
  • Seropositive and seronegative healthcare workers
• Study design
  • Asymptomatic healthcare staff: Invited to participate in voluntary PCR testing every 2 weeks and serologic testing every 2 months (beginning April 23, 2020)
  • Follow-up: 31 weeks
  • Primary outcomes were analyzed according to antibody status | Calculations adjusted for age, reported gender, and changes in incidence over time
• Primary outcome
  • PCR-positive SARS-CoV-2 test results
  • New symptomatic infections

RESULTS:

• 12,541 healthcare workers (HCWs)
  • Baseline negative antibody results: 11,364 HCWs
  • Baseline positive antibody results: 1265 HCWs
• Seronegative HCWs with a positive PCR test
  • Total: 223 HCWs (1.09 per 10,000 days at risk)
    • Asymptomatic at screening: 100 HCWs
    • Symptomatic at screening: 123 HCWs
• Seropositive HCWs with a positive PCR test
  • Total: 2 HCWs (0.13 per 10,000 days at risk)
    • Both were asymptomatic when tested
  • Adjusted incidence rate ratio 0.11 (95% CI, 0.03 to 0.44; P=0.002)
  • There were no symptomatic infections in HCWs with antibodies

CONCLUSION:

• SARS-CoV-2 reinfections in healthcare workers with antibodies were rare in the 31 weeks of follow-up
• The authors state

No symptomatic infections and only two PCR-positive results in asymptomatic health care workers were seen in those with anti-spike antibodies, which suggests that previous infection resulting in antibodies to SARS-CoV-2 is associated with protection from reinfection for most people for at least 6 months.

Learn More – Primary Sources:

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

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