First case of COVID-19 reinfection in US indicates exposure to virus may not lead to immunity: study

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TORONTO – U.S. researchers have confirmed the first case of COVID-19 reinfection in the country, indicating that exposure to the virus may not result in full immunity. The first study to confirm a case of coronavirus re-infection in the United States found evidence that an individual with no known immune disorder or underlying health condition was infected with SARS-CoV-2, the virus that causes the COVID-19, in two separate cases.

According to a new case study, published Monday in The Lancet, the 25-year-old Nevada man was infected with two different variants of SARS-CoV-2 within 48 days, while he was negative between each infection .

The researchers reported that the patient’s second infection was more severe, resulting in hospitalization with an oxygen supply.

Dr Mark Pandori, director of the Nevada State Public Health Laboratory, said the results indicate that previous exposure to COVID-19 does not mean that an individual guarantees full immunity to the disease. However, he says more research is needed.

“There are still many unknowns about SARS-CoV-2 infections and the immune system response, but our results indicate that a previous SARS-CoV-2 infection does not necessarily protect against future infection,” Pandori said in the study.

The patient was first diagnosed with COVID-19 in April, according to the study. He improved around April 27 and tested negative for the virus twice afterwards.

In June, after experiencing severe symptoms of COVID-19, including fever, headache, dizziness, cough, nausea and diarrhea, the patient was hospitalized and tested positive for the virus for a second time.

The genomes of the patient’s virus samples were sequenced in April and June, showing “significant genetic differences” between the two cases. Researchers say this implies that the patient was infected twice with two separate SARS-CoV-2 infections.

The study indicates that the patient has since been discharged from the hospital and has recovered from the second infection.

Pandori noted that all people, whether or not they have already been diagnosed with the novel coronavirus or not, should continue to take the necessary safety precautions to prevent infections such as physical distancing, wearing a face mask and hand washing.

“It is important to note that this is a singular discovery and does not allow this phenomenon to be generalized. Although more research is needed, the possibility of re-infections could have significant implications for our understanding of COVID-19 immunity, particularly in the absence of a vaccine, ”Pandori said.

The new case marks the fifth confirmation of re-infection of COVID-19 worldwide.

In August, researchers in Hong Kong said they found the first documented case of coronavirus reinfection in a 33-year-old man after testing positive for the disease twice in the past year.

At least three other cases of reinfection have since been confirmed in Belgium, the Netherlands and Ecuador. However, the researchers noted that only the case of re-infection in Ecuador had worse disease outcomes than the first infection.

The cases from Belgium and the Netherlands showed no difference in the severity of symptoms. In the case of Hong Kong, researchers said the man exhibited symptoms during his first episode of COVID-19, but had no obvious symptoms the second time around.

“We need more research to understand how long immunity can last for people exposed to SARS-CoV-2 and why some of these second infections, although rare, present as more serious,” Pandori said . “So far we’ve only seen a handful of cases of re-infection, but that doesn’t mean there aren’t more, especially since many cases of COVID-19 are asymptomatic. “

POSSIBLE CAUSES OF REINFECTION OF COVID-19

Researchers present several hypotheses in the study to potentially explain the severity of the second infection, including the possibility that the patient encountered a very high dose of the virus, causing a more acute reaction the second time around.

The study reported that the patient may also have come in contact with a “more virulent version of the virus”. Another hypothesis is that the presence of antibodies worsened the subsequent infection. The study indicates that this phenomenon, known as antibody-dependent enhancement, has been observed previously with beta-coronavirus SARS-CoV as well as other diseases, including dengue.

The authors explained that there is a “very slim possibility” of continued infection involving some form of deactivation and reactivation of anitbodies, but noted that proof of this hypothesis would require a SARS-CoV mutation rate. -2 which has not been observed at present.

According to the study, another explanation could be a simultaneous co-infection of the two strains of the virus. However, the researchers said that would mean the second strain was not detected in April and conversely, the first strain would have to be depleted before the June infection.

This possibility does not take into account the change in genotype in this patient, according to the study.

However, the authors acknowledged that there were some limitations to their study. The researchers say they were unable to undertake any evaluation of the immune response to the first episode of SARS-CoV-2 infection and were unable to fully assess the effectiveness of immune responses, such as than neutralization of antibody titers, during the second infection.

They also noted that this and other confirmed cases of reinfection have occurred in patients with symptoms of COVID-19. The study noted that it is possible for many infections and re-infections in individuals to be asymptomatic and likely go undetected under current global screening practices.

“Overall, there is a lack of full genomic sequencing of positive COVID-19 cases in the United States and around the world, as well as a lack of screening and testing, which limits the capacity of researchers and of public health officials to diagnose, monitor and obtain genetic follow-up for the virus, ”Pandori said.

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