First US COVID reinfection confirmed

The first US case of COVID-19 reinfection has been confirmed, taking the worldwide total of confirmed reinfection cases to five.

A 25-year-old US man was infected with two distinct SARS-CoV-2 variants within a 48-day period, according to new research published in the Lancet.

The man tested negatively between infections and had more severe symptoms, resulting in hospitalisation, the second time around.

More investigation into COVID immunity needed

Lead author Mark Pandori says there are still a lot of unknowns about our immune response to SARS-CoV2, and this case signals that previous infection may not necessarily protect against future infection.

“It is important to note this is a singular finding and does not provide generalisability of this phenomenon. While more research is needed, the possibility of reinfections could have significant implications for our understanding of 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.” Dr Pandori says.

At least four other reinfection cases have been confirmed, globally, in Belgium, the Netherlands Hong Kong, and Ecuador. However, only the Ecuador reinfection case displayed worse disease outcomes in the second infection, like the new US case.

This brings into question previous theories that immunity from infection may lead to milder symptoms if reinfection occurs, which may also have implications for vaccine development and herd immunity.

The researchers haven’t completely ruled out the possibility that the reinfection could actually be a continuous infection ‘involving some form of deactivation/reactivation’, but such a rate of mutation of SARS-C0V2 hasn’t been observed before, so it remains unlikely.

Another explanation could be a simultaneous infection of two strains of the virus, but this is also unlikely, the researchers say.

Understanding of COVID immunity vital for vaccine development

Yale University Immunobiology and Molecular, Cellular and Developmental Biology professor Akiko Iwasaki says research into reinfections will provide key information for effective vaccines and understanding the threshold for herd immunity.

The research is also important for us to better understand how infectious any people who are reinfected might be, Professor Iwasaki says.

Better and more comprehensive genomic screening of positive cases is needed, worldwide, to find other cases of reinfection, the researchers say.

Professor Iwasaki agrees, saying the rate of reinfection is still unknown.

“Due to the paucity of broad testing and surveillance, we do not know how frequently reinfection occurs among individuals who recovered from their first infection. Asymptomatic reinfection cases can only be picked up by routine community testing or at an airport, for example, and we are probably severely underestimating the number of asymptomatic reinfections.”