A 25-year-old man in the U.S. state of Nevada has contracted the coronavirus on two separate occasions, according to a study published in the Lancet Infectious Diseases Journal, adding another mystery to the novel coronavirus in terms of if an individual gains immunity long-term after infection.
The case published in the Lancet is the first confirmed case of SARS-CoV-2 reinfection in the U.S., adding to the few confirmed cases and speculations reported worldwide. The individual had first tested positive for the coronavirus in April with mild symptoms, recovered, and then tested positive again in early June with a more serious case of infection, according to the case report.
Researchers behind the peer-reviewed study documented that the individual had contracted the virus on two separate occasions due to his infections' genetic codes showing differences, meaning he was infected by two different strains of SARS-CoV-2.
"These findings suggest that the patient was infected by SARS-CoV-2 on two separate occasions by a genetically distinct virus. Thus, previous exposure to SARS-CoV-2 might not guarantee total immunity in all cases," the researchers behind the case study wrote.
The study's authors warned that based on the evidence presented in the case, "All individuals, whether previously diagnosed with COVID-19 or not, should take identical precautions to avoid infection with SARS-CoV-2."
While the case raises more questions than answers over immunity and potential vaccine effectiveness in the future, scientists believe that cases of reinfection are isolated incidents, meaning most individuals will only get infected once.
Brendan Wren, a professor of vaccinology at the London School of Hygiene & Tropical Medicine, told Reuters that the Nevada case was only the fifth conformed example of reinfection worldwide.
"The demonstration that it is possible to be reinfected by SARS-CoV-2 may suggest that a COVID-19 vaccine may not be totally protective," Wren stated in a comment to Reuters. "However, given the (more than) 40 million cases worldwide, these small examples of reinfection are tiny and should not deter efforts to develop vaccines."
With some world leaders advocating for herd immunity to be developed in their populations--either through infection or eventual vaccination--the unknown long-term extent of an individual's immunity may harm those efforts if put into practice.
World Health Organization Director-General Dr. Tedros Adhanom Ghebreyesus stated during a media briefing on Monday that herd immunity is not the answer to the pandemic, especially due to the lack of scientific knowledge on the strength and duration of any immune response to the coronavirus.
"Herd immunity is achieved by protecting people from a virus, not by exposing them to it," Tedros stated, disagreeing with the idea of letting the virus spread through a population as a way to eventually end the pandemic.
"Never in the history of public health has herd immunity been used as a strategy for responding to an outbreak, let alone a pandemic. It is scientifically and ethically problematic," he added. "Letting the virus circulate unchecked therefore means allowing unnecessary infections, suffering and death."
For now, the best tools a population has to mitigate the spread of the virus are facial coverings and social distancing.