Research has shown that antibody immunity for COVID-19 may only last only a few months, leaving people at risk for secondary infections.

But now there’s hope that T cells, the warrior lymphocyte cells in our bodies, may offer some protection against the disease now and in the future. And the good news is that many us have T cells that already recognize the coronavirus and can fend off an attack. This so-called hidden immunity may also be one of the keys to developing a vaccine for the disease.

According to BBC Future, T cells — not antibodies — may prove to be the vital link in the fight against COVID-19. T cells are white blood cells that identify and kill potential pathogen invaders. Researchers say that these cells have a long-term memory and can identify even past foes to mount a fast and effective response to an attacking virus.

Amazingly, researchers found that people had T cells that targeted the surface of the COVID-19 virus in blood samples taken before the pandemic began. In fact, 40-60% of these individuals had specific T cells that attacked the protein surfaces of the coronavirus. Scientists at the La Jolla Institute for Immunology in California found T cells that recognized and responded to SARS-CoV-2 in blood samples collected between 2015 and 2018.

Experts say the previous exposure to cold viruses may be how our immune systems develop T cells that respond to COVID-19. According to BBC Future, this means that T cells can provide protection for years and should be part of the overall plan to develop a vaccine.

“There is really an enormous spectrum of vaccine design,” said Adrian Hayday, an immunobiology professor at King’s College London, who added he was encouraged by the fact our immune systems easily recognize the virus. “And that really emphasizes how incredibly important these cells are — and that antibodies alone aren’t going to get you through.”