Strep throat is an unwanted but common hallmark of childhood.

What kid hasn’t had it at some point? Of course, adults can get strep throat, too, but for some children it seems to recur over and over again. Often, it brings with it the added problem of tonsillitis, which is an infection of the pad-like tissue formations at the back of the throat. The tonsils fight off microorganisms that get into the mouth, but can themselves become infected.

Strep throat and tonsillitis both cause fever, intense throat pain and swollen glands in the neck and throat.

Generations of parents have wondered why some kids have recurring cases of strep and tonsillitis. New research published in the journal Science Translational Medicine uncovered factors that seem likely to contribute to the problem.

The study’s authors examined tissue samples from nearly 150 children who had their tonsils removed, some due to repeat strep throat and some due to sleep apnea. They found kids who had repeat strep and tonsillitis had smaller germinal centers in their tonsils. Germinal centers are areas within the tonsils where immune system cells reproduce and prepare for battle against invading organisms.

Other differences included fewer numbers of certain immune cells within the tonsils, lower blood levels of antibodies that help fight the strep bacteria, and genetic variations that increased vulnerability to the disease.

Altogether, these children had a weaker-than-normal immune response to strep throat.

These findings give science clues that may one day lead to a vaccine for strep throat, which would be cause for celebration for parents and children alike.