Broad humoral and cellular immunity elicited by one-dose mRNA vaccination 18 months after SARS-CoV-2 infection

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Authors: Chang Kyung Kang ; Hyun Mu Shin ; Pyoeng Gyun Choe ; Jiyoung Park ; Jisu Hong ; Jung Seon Seo ; Yung Hie Lee ; Euijin Chang ; Nam Joong Kim ; Minji Kim ; Yong-Woo Kim ; Hang-Rae Kim ; Chang-Han Lee ; Jun-Young Seo ; Wan Beom Park ; Myoung-Don Oh

MeSH: Antibodies, Viral ; COVID-19 Testing ; COVID-19 Vaccines ; COVID-19* / prevention & control ; Humans ; Immunity, Cellular ; RNA, Messenger / genetics ; SARS-CoV-2* / genetics ; Vaccination ; Vaccines, Synthetic ; mRNA Vaccines

Abstract: Background: Practical guidance is needed regarding the vaccination of coronavirus disease 2019 (COVID-19) convalescent individuals in resource-limited countries. It includes the number of vaccine doses that should be given to unvaccinated patients who experienced COVID-19 early in the pandemic.

Methods: We recruited COVID-19 convalescent individuals who received one or two doses of an mRNA vaccine within 6 or around 18 months after a diagnosis of severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) infection. Their samples were assessed for IgG-binding or neutralizing activity and cell-mediated immune responses against SARS-CoV-2 wild-type and variants of concern.

Results: A total of 43 COVID-19 convalescent individuals were analyzed in the present study. The results showed that humoral and cellular immune responses against SARS-CoV-2 wild-type and variants of concern, including the Omicron variant, were comparable among patients vaccinated within 6 versus around 18 months. A second dose of vaccine did not significantly increase immune responses.

Conclusion: One dose of mRNA vaccine should be considered sufficient to elicit a broad immune response even around 18 months after a COVID-19 diagnosis.