The coronavirus quarantine might last far longer than expected.

A new study suggests that individual immunity to COVID-19 may not last more than a couple of months, meaning that a person could become reinfected. It’s a possibility that – if true – will have sobering implications for our ability to contain the pandemic.

The paper, which has not yet been peer reviewed, was posted last week in the preprint server medRxiv. After pointing out that antibodies to the virus that causes COVID-19, SARS-CoV-2, are usually detectable within 10 to 15 days after a person begins exhibiting symptoms, the researchers note that it is unclear how long these antibodies will last and whether they immunize patients from being infected again.

To ascertain whether the antibodies that can neutralize the virus (nAbs) persist long enough to provide lasting protection, a group of scientists studied blood samples taken over time from 65 people who tested positive for the coronavirus — whose conditions ranged from asymptomatic to life-threatening — over a period of up to 94 days after they initially displayed symptoms.

They found that more than 95% of the studied patients had developed the antibodies and carried nAbs roughly eight days after they were diagnosed, with nAb levels peaking after an average of 23 days. The nAb levels soon began to drop, however, and among patients who were tested after 65 days, the number who retained potent nAbs fell to 16.7%. Patients with higher nAb levels at their peak maintained them after more than 60 days, while those who did not have higher levels wound up returning almost to their baseline. These findings were reinforced by a similar study the researchers conducted  of 31 healthcare workers at a different group of British hospitals.