The virus that causes COVID-19 was only discovered a few months ago, so there’s a lot we’re still learning about it. A few stories coming out of China, Japan, and South Korea of people testing positive for the virus after recovery have a lot of people asking if it’s possible to be reinfected with COVID-19.
Based on data from other viruses and coronavirus strains, we know that people make antibodies 7-10 days after infection and that, depending on the type of virus, these antibodies can fend off reinfection for months to years after recovery (antibodies provide immunity only to the specific strain of coronavirus that a person was infected with). But, again, since COVID-19 is a new virus, we still don’t know how long antibodies will stay in our system after this specific viral infection.
Does being infected with COVID-19 make you immune?
We will need to do long-term studies in humans to find out if people who recover from COVID-19 are immune and to learn how long that immunity will last. But again, based on what we know about how our bodies respond to other viruses, it is highly likely that the antibodies we make after infection with the COVID-19 virus will provide immunity for a period of time.
Chinese scientists have conducted some early research with rhesus monkeys and found that antibodies after recovery from COVID-19 protected the monkeys from becoming reinfected after another exposure to the virus. After the SARS outbreak, one study showed antibodies lasted for up to 3 years. Studies from Middle East Respiratory Virus (MERS), another infection caused by a coronavirus, have shown that antibodies can be found in the body for about a year.
The level and time period of immunity can also depend on how an individual’s immune system responds, so there is a lot more we still need to learn about immunity after COVID-19 infection.
Can you get reinfected after recovering from COVID-19?
Some reports have started to emerge about people who have recovered from COVID-19, but later tested positive for the virus again.
Several reports from China have described cases of people with mild symptoms continuing to test positive for the virus, even after recovery. A small study of Chinese healthcare workers also described findings where people continued to test positive even after they had recovered. The study found that these individuals no longer had symptoms and that they didn’t go on to infect their family members. Very recently, the Korean Centers for Disease Control also reported dozens of people that tested positive after recovery.
Two cases outside of China are even more puzzling: people who had seemingly recovered and tested negative, then weeks later, began to have symptoms again and were found to be positive when re-tested.
According to experts, these scenarios require further study, but are unlikely to reflect reinfection. A positive test after recovery could be detecting left over virus that may still be present but is not causing infection. For those people who became positive after recovery, it may be that the infection was lingering in their bodies at lower levels and then re-emerged. Or it could mean that prior negative test were false negative (the swab may not have captured viral particles during the testing process).
Research will continue to look at this question, but from what we know about our body’s ability to fight of viruses, it is highly unlikely that a person that has recovered from COVID-19 and made antibodies will become reinfected in such a short period of time.