Vaccine-breakthrough infection by the SARS-CoV-2 Omicron variant elicits broadly cross-reactive immune responses

Zhou, R.; To, K. K.-W.; Peng, Q.; Chan, J. M.-C.; Huang, H.; Yang, D.; Lam, B. H.-S.; Chuang, V. W.-M.; Cai, J.-P.; Liu, N.; Au, K.-K.; Tsang, O. T.-Y.; Yuen, K.-Y.; Chen, Z.

doi:10.1101/2021.12.27.474218

bioRxiv · 10.1101/2021.12.27.474218

Vaccine-breakthrough infection by the SARS-CoV-2 Omicron variant elicits broadly cross-reactive immune responses

Zhou, R.·To, K. K.-W.·Peng, Q.·Chan, J. M.-C.·Huang, H.·Yang, D.·Lam, B. H.-S.·Chuang, V. W.-M.·Cai, J.-P.·Liu, N.·Au, K.-K.·Tsang, O. T.-Y.·Yuen, K.-Y.·Chen, Z.

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Abstract

Highly transmissible SARS-CoV-2 Omicron variant has posted a new crisis for COVID-19 pandemic control. Within a month, Omicron is dominating over Delta variant in several countries probably due to immune evasion. It remains unclear whether vaccine-induced memory responses can be recalled by Omicron infection. Here, we investigated host immune responses in the first vaccine-breakthrough case of Omicron infection in Hong Kong. We found that the breakthrough infection rapidly recruited potent cross-reactive broad neutralizing antibodies (bNAbs) against current VOCs, including Alpha, Beta, Gamma, Delta and Omicron, from unmeasurable IC50 values to mean 1:2929 at around 9-12 days, which were higher than the mean peak IC50 values of BioNTech-vaccinees. Cross-reactive spike- and nucleocapsid-specific CD4 and CD8 T cell responses were detected. Similar results were also obtained in the second vaccine-breakthrough case of Omicron infection. Our preliminary findings may have timely implications to booster vaccine optimization and preventive strategies of pandemic control.

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Zhou, R., To, K. K.-W., Peng, Q., Chan, J. M.-C., Huang, H., Yang, D., Lam, B. H.-S., Chuang, V. W.-M., Cai, J.-P., Liu, N., Au, K.-K., Tsang, O. T.-Y., Yuen, K.-Y., Chen, Z.. 2021-12-28. Vaccine-breakthrough infection by the SARS-CoV-2 Omicron variant elicits broadly cross-reactive immune responses. https://doi.org/10.1101/2021.12.27.474218

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