Concern over the Omicron variant and the vaccine's efficacy grows as the current vaccines are mainly designed against SARS-CoV-2's spike proteins, and Omicron carries several mutations on the spike protein. But the recent trend of a relatively large number of people getting infected with Omicron, albeit with milder symptoms, prompted scientists to look deeper beyond the widely studied neutralizing antibody response.
Evidence from around the world suggests that the immunity elicited by specialized immune cells called T-cells, which provide relatively longer protection than antibodies, can counter variants of the SARS-CoV-2 virus – including the Omicron variant. There was such an indication from the beginning as T-cell responses correlated with increased protection against severe diseases caused by Omicron following vaccination with Pfizer and Johnson & Johnson vaccines despite lower levels of Omicron-neutralizing antibodies.
The good news is that the T-cell levels do not seem to fade as quickly as antibodies following an infection or vaccination, and they can recognize many more sites along the spike protein than can antibodies – enabling it to recognize even the highly mutated variants like Omicron, thus providing enduring immunity.
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