Post-vaccination T cell immunity to omicron

Abstract

In late 2021, the omicron variant of SARS Coronavirus 2 (SARS-CoV-2) emerged and replaced the previously dominant delta strain. Effectiveness of COVID-19 vaccines against omicron has been challenging to estimate in clinical studies or is not available for all vaccines or populations of interest. T cell function can be predictive of vaccine longevity and effectiveness against disease, likely in a more robust way than antibody neutralization. In this mini review, we summarize the evidence on T cell immunity against omicron including effects of boosters, homologous versus heterologous regimens, hybrid immunity, memory responses and vaccine product. Overall, T cell reactivity in post-vaccine specimens is largely preserved against omicron, indicating that vaccines utilizing the parental antigen continue to be protective against disease caused by the omicron variant.

Keywords: COVID-19; SARS-CoV-2; T cell; omicron; vaccine.

Figure 1

Overview of study results on omicron-specific T cell reactivity compared to the parental strain of SARS-CoV-2. Study results from 13 studies assessing omicron-specific T cell reactivity available by March 31^st, 2022, are shown as fold-change compared to parental-specific T cell activation. Non peer-reviewed pre-prints are shown as squares. A) Data on primary vaccine regimen and B) data on booster regimen. Every data point represents a single study. Data points from the same study are depicted with the same color. Data are either presented within the manuscript or abstracted from high-resolution figures or raw data provided with the manuscript. “Primary regimen (any vaccine)” and “Boost regimen (any vaccine) show all data points from studies on primary or boost vaccine cohorts, respectively (dark grey bars), excluding hybrid immunity shown in a separate bar (shaded bars). Data are not stratified for sampling intervals and peak-immunity as well as waned immunity data sets are included. Bars indicate the median fold-change in T cell cross-reactivity to omicron, compared to the parental strain. N.d, no data.