As of June 8, more than 7.11 million people worldwide have contracted COVID-19. Nearly half of them have recovered, but now they are looking to the future and wondering: what happens when they encounter the SARS-CoV-2 virus again?
Reinfection is a major concern in the U.S and around the globe, especially since scientists still don’t fully understand the body’s immune function against the novel coronavirus. Here’s what we do know so far.
How Does the Body Develop Immunity to COVID-19?
The body’s defense system consists of two components of the immune system. The first part of the immune system triggers the release of chemicals as soon as a foreign invader is detected. Those chemicals cause white blood cells and inflammation to destroy infected cells.
Next, the adaptive immune response piece of the immune system produces targeted antibodies that stick to the virus or infection. Antibodies are powerful substances inherently designed to block specific, targeted sources of infection. It can take 10 days or more for the body’s immune system to generate antibodies tailored to attack the coronavirus.
The question is, how long will the adaptive immune response be able to identify the SARS-CoV-2 infection in order to trigger the production of coronavirus antibodies if needed in the future? If COVID-19 affects the immune system like measles, it may become built into the memory of the immune system for life. On the other hand, if COVID-19 is quickly forgotten like the common cold or RSV, re-infection could occur after just weeks or months.
Researchers Look to Other Coronaviruses For Insight
Without the benefit of time, researchers can’t yet establish how long immunity lasts. “The question is not whether you become immune, it’s how long for,” explained Paul Hunter, a professor in medicine at the University of East Anglia.
Experts hope to find some answers by examining the behavior of other known coronavirus diseases, including 229E, OC43, NL63, and HKU1. According to Jeffrey Shaman, PhD, senior author of new research through Columbia University School of Public Health, “The evidence from endemic coronaviruses suggests that immunity is short-lived and re-infection is common within one year, with symptom severity possibly more a function of genetics than the presence or absence of antibodies.”
There’s no guarantee that SARS-CoV-2 will behave the same as endemic coronaviruses, but Shaman’s research provides a useful reference for preparing for the risk of repeat infection with COVID-19.
False Positives of Reinfection in South Korea Caused Panic
In mid-April, reports from South Korea sparked worldwide panic when more than 260 people who had recovered from the coronavirus suddenly retested positive. However, the World Health Organization later reported the reports of reinfection were actually false positives.
It turns out that the coronavirus testing process identified remnants of the dead virus in patients’ lungs, creating a false positive.
Dr Joshua Schiffer, an expert in infectious diseases at Fred Hutchinson Cancer Research Center in the US, explains that confirming re-infection isn’t nearly as simple as an on-demand COVID-19 test.
“I have yet to see a definitive case of reinfection reported in the scientific literature [to date]. To truly prove reinfection, and discriminate from prolonged viral shedding related to the first infection, would require sequencing of both the first and second viruses and demonstration that the two viruses are genetically different,” he said, adding it will also be important to look at symptoms and how long reinfection lasts.
Sources
- http://www.columbia.edu/~jls106/galanti_shaman_ms_supp.pdf
- https://www.publichealth.columbia.edu/public-health-now/news/risk-coronavirus-reinfection-remains-after-recovery
- https://www.bbc.com/news/health-52446965
- https://www.statista.com/statistics/1087466/covid19-cases-recoveries-deaths-worldwide/
- https://www.businessinsider.com/coronavirus-south-korean-reactivated-cases-not-reinfected-experts-2020-4