COVID-19 reinfection casts doubt on virus immunity

The new figure of 1,539 is still almost five times lower than an April 8 high of 7,148

"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".

According to the scientists, including those from the University of Nevada in the USA, 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 Nevada case is the fifth confirmation of COVID-19 reinfection globally.

The patient's second bout of COVID-19 was worse than the first, requiring hospitalization and assistance in breathing, the study said.

In particular, it could influence the hunt for a vaccine - the now Holy Grail of pharmaceutical research.

Researchers at CSIRO, Australia's national science agency, have found that the virus responsible for Covid-19, can survive for up to 28 days on common surfaces including banknotes, mobile phone screens and stainless steel.

"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", he said.

Vaccines work by triggering the body's natural immune response to a certain pathogen, arming it with antibodies it to fight off future waves of infection.

"Among Italy, Spain, and Japan, the age distributions of COVID-19 mortality show only small variation even though the number of deaths per country shows large variation, "the team writes in their new paper".

Another possibility is that the presence of antibodies in his bloodstream made the second infection worse; this phenomenon has been observed in other diseases such as dengue fever.

To date, researchers have confirmed only 23 cases of reinfection, but in all prior cases the patient recovered.

US President Donald Trump tosses a face mask to the crowd as he takes the stage for a campaign rally, his first since being treated for the coronavirus disease, at Orlando Sanford International Airport in Sanford, Florida, US [Jonathan Ernst/Reuters] The report was published just hours after US President Donald Trump, who was infected with COVID-19 and hospitalised earlier this month, said he believes he now has immunity and felt "so powerful". Scientists said that the man had contracted the virus for a second time rather than his infection growing stronger.

Alternatively, it may have been a more virulent strain of the virus. "Thus, previous exposure to SARS-CoV-2 might not guarantee total immunity in all cases", the study's authors said.

"This information is key to understanding which vaccines are capable of crossing that threshold to confer individual and herd immunity", added Iwasaka, who was not involved in the study.