Scientists have charted how the antibodies of a person infected with Ebola virus evolve over time — and the findings suggest that survivors remain protected from the disease for at least three years after recovery.

Infection with Ebola virus triggers immune cells to produce antibodies, which work to fight off the pathogen. Rafi Ahmed at Emory University in Atlanta, Georgia, and his colleagues assessed antibodies in four people who were treated for Ebola at Emory’s hospital in 2014, during an outbreak of the disease in West Africa.

The team found that one set of antibodies surged acutely after infection. Over the next three years, those antibodies diminished in number in all four patients, whereas other antibody subsets rose. Pockets of virus hiding in the eyes and testicles, and viral fragments in lymph nodes, might have triggered production of the later Ebola-fighting antibodies — but they did not cause the disease to recur.

In the future, researchers might be able to﻿ determine whether an Ebola vaccine offers protection by analysing whether it elicits the same antibodies that survivors of the disease developed within six months of an infection.