Influence of past infection with SARS-CoV-2 on the response to the BNT162b2 mRNA vaccine in health care workers: Kinetics and durability of the humoral immune response

Background: SARS-CoV-2 vaccines are an invaluable resource against COVID-19. Current vaccine shortage makes it necessary to prioritize distribution to the most appropriate segments of the population. Methods: This is a prospective cohort study of 63 health care workers (HCWs) from a General Hospital. We compared antibody responses to two doses of BNT162b2 mRNA COVID-19 vaccine between HCWs with previous SARS-CoV-2 infection (experienced HCWs) and HCWs without previous infection (naive HCWs). Findings: Seven days after the first vaccine dose, HCWs with previous infection experienced a 126-fold increase in antibody levels (p<0.001). However, in the HCW naive group, response was much lower and only five showed positive antibody levels (>50 AU). After the second dose, no significant increase in antibody levels was found in experienced HCWs, whereas in naive HCWs, levels increased by 16-fold (p<0.001). Approximately two months post-vaccination, antibody levels were much lower in naive HCWs compared to experienced HCWs (p<0.001). Interpretation: The study shows that at least ten months post-COVID-19 infection, the immune system is still capable of producing a rapid and powerful secondary antibody response following one single vaccine dose. Additionally, we found no further improvement in antibody response to the second dose in COVID-19 experienced HCWs. Nonetheless, two months later, antibody levels were still higher for experienced HCWs. These data suggest that immune memory persists in recovered individuals; therefore, the second dose of the COVID-19 vaccine in this group could be postponed until immunization of the remaining population is complete. (C) 2021 The Author(s). Published by Elsevier B.V.

Automated summary

The study shows that at least ten months post-COVID-19 infection, the immune system is still capable of producing a rapid and powerful secondary antibody response following one single vaccine dose. There was a significant increase in antibody levels after the second dose in naive HCWs, while experienced HCWs showed no further improvement in antibody response to the second dose.