COVID-19 patients infected with the novel coronavirus for a second time
might experience more severe symptoms, according to a study which is the
first to confirm a case of reinfection with the virus in the US.
The study, published in the journal Lancet Infectious Diseases, found
evidence that an individual with no known immune disorders or underlying
conditions was infected with the SARS-CoV-2 virus in two separate
occurrences.
According to the scientists, including those from the University of Nevada
in the US, the patient, a 25-year old male, was infected with two distinct
SARS-CoV-2 variants within a 48-day time frame, while testing negative in
between infections.
The study noted that the patient's second infection was more severe,
resulting in hospitalisation with oxygen support, indicating previous
exposure to COVID-19 may not translate to guaranteed total immunity.
The patient tested negative for the virus after testing positive for
SARS-CoV-2 in April 2020, the researchers said.
Then in June 2020, after experiencing severe COVID-19 symptoms, including
fever, headache, dizziness, cough, nausea, and diarrhea, the patient was
hospitalised and tested positive for a second time.
The patient has since been discharged from the hospital and has recovered
from the second infection, the study noted.
While further research into reinfections is required, the scientists
believe all individuals -- whether previously diagnosed or not -- should
take identical precautions to prevent infection with SARS-CoV-2.
"There are still many unknowns about SARS-CoV-2 infections and the immune
system's response, but our findings signal that a previous SARS-CoV-2
infection may not necessarily protect against future infection," said Mark
Pandori, lead author of the study from the University of Nevada.
"It is important to note this is a singular finding and does not provide
generalisability of this phenomenon," Pandori said.
While more research is needed, the scientists said the possibility of
reinfections could have significant implications for understanding
COVID-19 immunity, especially in the absence of an effective vaccine.
"It also strongly suggests that individuals who have tested positive for
SARS-CoV-2 should continue to take serious precautions when it comes to
the virus, including social distancing, wearing face masks, and
handwashing," Pandori explained.
According to the scientists, at least four other reinfection cases have
been confirmed globally in Belgium, the Netherlands, Hong Kong, and
Ecuador with the latter being the only other instance in which the second
infection displayed worse disease outcomes than the first.
"We need more research to understand how long immunity may last for people
exposed to SARS-CoV-2, and why some of these second infections, while
rare, are presenting as more severe," Pandori said.
"So far, we've only seen a handful of reinfection cases, but that doesn't
mean there aren't more, especially as many cases of COVID-19 are
asymptomatic. Right now, we can only speculate about the cause of
reinfection," he added.
The study noted several hypotheses that may explain the severity of the
second infection, including the possibility the patient subsequently
encountered a very high dose of the virus which caused a more acute
reaction the second time.
According to the researchers, the patient may also have come in contact
with a more virulent variant of the virus.
They said another plausible explanation could be the mechanism of antibody
dependent enhancement in which some protective proteins produced by the
immune system during the first encounter with the virus could make a
subsequent infection worse.
This mechanism, the researchers noted, was seen previously with the
2002-03 SARS pandemic virus, as well as other diseases, such as dengue
fever.
Citing the limitation of the study, the researchers said they were unable
to undertake any evaluation of the immune response to the first episode of
infection.
Since the confirmed reinfection cases occurred among patients who
displayed COVID-19 symptoms, the scientists believe there is a possibility
that many similar cases among individuals may be asymptomatic, and
therefore likely to remain undetected under current testing and monitoring
practices.
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Reference:
What reinfections mean for COVID-19
Published:October 12, 2020