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Coronaviruses

COVID-19 Vaccine Efficacy in Previously Infected Healthcare Workers

Strategic Insights

— 1 min read

Researchers at the INT-IRCCS "Fondazione Pascale" Cancer Center in Naples, Italy, have conducted a retrospective study to evaluate the humoral immune response to the SARS-CoV-2 spike mRNA vaccine (BNT162b2/Pfizer) in two cohorts of healthcare workers: those previously infected with SARS-CoV-2 and those who were not. The study, published in Infectious Agents and Cancer, aimed to determine the immune response to the vaccine after one and two doses in both groups. The results showed that previously infected healthcare workers developed a significant immune response after the first dose, whereas those who were not infected took longer to develop a substantial response.

Key Takeaways:

  • Pre-existing immunity in previously infected healthcare workers resulted in a significantly higher immune response after the first dose of the SARS-CoV-2 vaccine.
  • Not infected healthcare workers showed a lower immune response after the first dose but reached a similar level of immunity after the second dose.
  • The study suggests that individuals who have been previously infected with SARS-CoV-2 may only require one dose of the vaccine to achieve adequate immunity.
  • The geometric mean titers and relative fold changes (FC) in antibody responses were calculated, and the results showed that the FC for previously infected subjects was very modest due to the high basal antibody titer.
  • Conversely, not infected subjects showed a lower mean fold change following the first dose, reaching 3.8 FC in 72 subjects (45.6%) after the second dose.
  • The authors propose that the possibility of administering only one dose of the vaccine in previously SARS-CoV-2-infected individuals warrants further investigation.

Statistics:

  • 35 healthcare workers with a previous documented history of SARS-CoV-2 infection were included in the study.
  • 158 healthcare workers without COVID-19 were also part of the study.
  • The study showed a geometric mean titer of 2500.0 BAU/mL in the Roche Elecsys Anti-SARS-CoV-2 S immunoassay.
  • Fold changes (FC) were calculated for both previously infected and not infected subjects.

Sources:

  • Vaccination Strategy and Anti - Sars-cov-2 S Titers In Healthcare Workers of the Int - Irccs "fondazione Pascale" Cancer Center (Naples, Italy). Infectious Agents and Cancer, 2021;16(1).
  • Infectious Agents and Cancer can be contacted at: Bmc, Campus, 4 Crinan St, London N1 9XW, England. (BioMed Central - www.biomedcentral.com/; Infectious Agents and Cancer - www.infectagentscancer.com)

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