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“This is exactly what you would hope for,” said Marion Pepper, an immunologist at the University of Washington and an author on another of the new studies, which is currently under review at the journal Nature. “All the pieces are there to have a totally protective immune response.”

Protection against reinfection cannot be fully confirmed until there is proof that most people who encounter the virus a second time are actually able to keep it at bay, Dr. Pepper said. But the findings could help quell recent concerns over the virus’s ability to dupe the immune system into amnesia, leaving people vulnerable to repeat bouts of disease.

Researchers have yet to find unambiguous evidence that coronavirus reinfections are occurring, especially within the few months that the virus has been rippling through the human population. The prospect of immune memory “helps to explain that,” Dr. Pepper said.

In discussions about immune responses to the coronavirus, much of the conversation has focused on antibodies — Y-shaped proteins that can latch onto the surfaces of pathogens and block them from infecting cells. But antibodies represent just one wing of a complex and coordinated squadron of immune soldiers, each with their own unique modes of attack. Viruses that have already invaded cells, for instance, are cloaked from antibodies, but are still vulnerable to killer T cells, which force infected cells to self-destruct. Another set of T cells, nicknamed “helpers,” can coax B cells to mature into antibody-making machines.

(Yet another sector of the immune system assails pathogens within minutes of their arrival, while sending out signals called cytokines to mobilize forces from elsewhere in the body. Some evidence suggests that severe cases of Covid-19 may stem from this early process going awry.)