Can we be reinfected with COVID-19 after recovery?

A key question in the COVID-19 pandemic has been whether we can be re-infected with the virus after recovering.

There have been anecdotal reports of people getting infected twice, but wasn’t hasn’t been clear is whether they really cleared the virus the first time round and got infected again, or whether they never really cleared the virus in the first place.

A study published yesterday from Hong Kong showed definitively that a 33-year-old man was re-infected.

They established this by sequencing the virus isolated from his first positive test, and comparing that viral genetic sequence to his second positive test (approx. 4.5 months later).

Importantly, during the second infection, the man showed no symptoms. This is how we expect immunity to work: even if we can get re-infected, our immune system is able to respond quickly enough because of its existing antibodies and T cells so that we don’t get sick.

Even though the man showed no symptoms, he was still infectious – meaning he could still transmit the virus, which means that herd immunity through natural infection may not be the best approach.

Vaccines are designed to mimic that first natural infection, but we expect and hope that they will protect us from getting symptoms AND from transmitting the virus.

More widespread studies are needed to establish how common this re-infection is and how it affects people of different age groups and risk factors.

Last updated:
3 September 2020