A 33-year-old man from Hong Kong tested positive for the novel coronavirus for the second time in just over four months, according to preliminary research, raising questions about long-term immunity from COVID-19.
“This is the world’s first documentation of a patient who was thought to have previously recovered from COVID-19 but got another episode afterward,” a team of medical researchers from the University of Hong Kong (HKU) said in a preliminary report due to be published in the peer-reviewed Clinical Infectious Diseases medical journal.
The researchers wrote that they had sequenced the genetic makeup of the virus on both occasions and discovered that the patient’s most recent infection was likely not tied to the first.
During the man’s first bout with COVID-19 in March, researchers say he had a sore throat, headache, cough, and fever for three days before a subsequent test yielded a positive result for COVID-19. The otherwise healthy man was hospitalized for two weeks and was later discharged after testing negative for the virus.
Researchers wrote that the man tested positive for the virus again in August after he returned from a trip to Spain via the United Kingdom. This time, he presented as asymptomatic.
“This case illustrates that re-infection can occur even just after a few months of recovery from the first infection,” HKU researchers wrote, adding that the findings also suggest that COVID-19 “may persist in humans, as is the case for other common cold-associated human coronaviruses, even if patients have acquired immunity via natural infection or vaccination.”
“It is unlikely that herd immunity can eliminate SARS-CoV-2, although it is possible that subsequent infections may be milder than the first as for this patient,” they added.
The research comes as mutated strains of the coronavirus have recently been detected by health authorities in Malaysia and the Philippines.
There have been other anecdotal reports of coronavirus reinfections elsewhere in the world.
The World Health Organization (WHO) on Monday, August 24, warned against jumping to conclusions based on the preliminary research.
“What we are learning about infection is that people do develop an immune response and what is not completely clear yet is how strong that immune response is and for how long that immune response lasts,” Maria Van Kerkhove, an infectious disease epidemiologist, said at the WHO media briefing on Monday addressing the latest case in Hong Kong.
“What I think is really important is that we put this into context,” she added. “There've been more than 24 million cases reported to date, and we need to look at something like this at a population level.”
Singaporean doctor and professor of infectious diseases Paul Tambyah said that while the virus continues to evolve, current medical knowledge was also “expanding exponentially”.
“Health professionals around the world are able to apply what we know about the virus to help contain it but this case from Hong Kong was an unusual one where an individual did not develop an immune response despite a full recovery,” Tambyah told VICE News.
“It might have been because his initial infection was very mild. But these cases do rarely occur with other viruses as there are individuals who have had chickenpox or measles twice.”
The Hong Kong University researchers wrote in their preliminary research that even those who have already recovered from the coronavirus should still get vaccinated when a vaccine becomes available. They added that people should still comply with measures to prevent the coronavirus spread, like wearing a mask and social distancing.
Experts say that these measures, along with continued testing and contact tracing, will protect against new clusters in the future as we continue to learn more about the coronavirus spreads.
“The key for COVID-19 is to find these people and make sure that they do not trigger off new clusters among those who have never been infected,” Tambyah said. “And with major advances in diagnosis and better tests becoming more widely available, we now know about which drugs are effective at new stages of the disease.”