(Reuters) – In some patients on immunosuppressive drugs, COVID-19 vaccines may induce protective antibodies without inducing good second-line immune defenses, leaving them at risk for severe illness if they do become infected, researchers say.

In 303 patients on immune-suppressing therapies for inflammatory bowel disease, researchers used a new molecular measurement tool to count the numbers of antiviral T cells induced by COVID vaccines. “Overall, a substantial number of vaccinated patients – about 20% – had minimal antiviral T cell levels, even though most had high antiviral antibodies,” study leader Jonathan Braun of Cedars-Sinai Medical Center in Los Angeles told Reuters.

Age, sex and specific immunotherapies might be associated with patients’ T-cell response to the vaccines, but the bottom line is that antibody levels after vaccination do not necessarily predict T cell responses, his team said in a report posted on medRxiv ahead of peer review.

Levels of antiviral T cells are not often measured, Braun said, leaving open important questions. Among them: How frequent are vaccinated individuals with low antiviral T cell levels in the general population? and, Do boosters help such individuals elevate their antiviral T cell levels?

SOURCE: https://bit.ly/3GM778d medRxiv, online December 8, 2021.

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