• 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, and Myoung-Don Oh.
• Department of Internal Medicine, Seoul National University College of Medicine, Seoul, 03080, South Korea.
• Bmc Med. 2022 May 4; 20 (1): 181181.

BackgroundPractical 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.MethodsWe 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.ResultsA 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.ConclusionOne dose of mRNA vaccine should be considered sufficient to elicit a broad immune response even around 18 months after a COVID-19 diagnosis.© 2022. The Author(s).

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