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Case Reports
. 2023 Apr 18;227(8):1002-1006.
doi: 10.1093/infdis/jiac409.

Residual Humoral Immunity Sustained Over Decades in a Cohort of Vaccinia-Vaccinated Individuals

Conrad E Z Chan  1   2 , Steven K K Wong  2 , Nurhidayah Binte M Yazid  1 , Oon Tek Ng  1   3   4 , Kalisvar Marimuthu  1   3   5 , Monica Chan  1   3 , Hwee Siew Howe  1   4 , Yee-Sin Leo  1   3   4   5 , Bernard P Leung  3   5   6 , Shawn S Vasoo  1   3   4 , Barnaby E Young  1   3   4
Affiliations
Case Reports

Residual Humoral Immunity Sustained Over Decades in a Cohort of Vaccinia-Vaccinated Individuals

Conrad E Z Chan et al. J Infect Dis. .

Abstract

Serological testing of Singaporeans who received childhood smallpox vaccination found anti-vaccinia IgG binding and neutralizing activity indicating long-term humoral immunity. There was correlation between IgG and neutralizing titers indicating IgG could be used as a surrogate marker for humoral immunity. In 2019, Singapore experienced a case of imported monkeypox. As with smallpox, disease can be prevented through vaccination, which was mandatory for Singaporean infants until 1981. However, the degree of residual immunity in older vaccinated Singaporeans remains unknown. Sera from individuals born 1946-1984 were therefore tested and those born prior to 1981 were found to have higher anti-vaccinia IgG and neutralizing activity titers. This suggests that protective humoral immunity remains, which could reduce disease severity in an orthopoxvirus outbreak. Correlation between IgG and neutralizing titers was observed indicating that serology could be used as a surrogate marker for immunity.

Keywords: monkeypox; smallpox; vaccinia.

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Conflict of interest statement

Potential conflicts of interest. All authors: No reported conflicts of interest. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed.

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