Elon Musk has again tested positive for Covid-19. 

The billionaire CEO is part of a rising trend of people getting hit with Covid-19, despite previously recovering from the virus. 

Space X and Tesla CEO has tested positive for the second time, after he was previously infected in November 2020. 

"Covid-19 is the virus of Theseus," he tweeted. 

"How many gene changes before it's not Covid-19 anymore? 

"I supposedly have it again (sigh), but almost no symptoms." 

The tech-billionaire is part of a rising trend of people who are reporting reinfection of Covid-19. 

White House Press Secretary, Jen Psaki was also recently reinfected with Covid, five months after her first infection. 

Confirming the news on Twitter, meant Psaki had to cancel her Europe trip with US President Joe Biden. 

"Today, in preparation for travel to Europe, I took a PCR test this morning. That test came back positive, which means I will be adhering to CDC guidance and no longer be travelling on the President's trip to Europe," she tweeted. 

"Thanks to the vaccine, I have only experienced mild symptoms. 

"In alignment with White House Covid-19 protocols, I will work from home and plan to return to work in person at the conclusion of a five-day isolation period and a negative test." 

Although becoming reinfected with Covid-19 is rare, the immunity that comes with recovering from Covid generally wears off after four months, said the head of Australia's Therapeutic Goods Administration (TGA), Professor John Skerritt. 

Speaking to reporters in February, he quotes UK research which said one in 24 people who recover from Covid become reinfected with the virus. 

According to NSW Health, most people have a low risk of contracting Covid-19 in the 28 days after isolation. 

Studies also suggest you're less likely to be re-infected with the Omicron BA. 2 sub-variant if you've previously had Omicron BA.1. People who have previously recovered from the Delta variant are more likely to suffer reinfection with the Omicron strain. 

A study published in The New England Journal of Medicine confirmed that while the previous infection offered "robust" protection against the alpha (90.2 per cent), beta (85.7 per cent) and delta (92 per cent) variants, it only offered 56 per cent protection against the Omicron variant. 

However, those who did become reinfected were less likely to need hospitalisation or die of the virus. 

While there aren't exact figures around exactly how many people are getting reinfected with Covid, a spokesperson for NSW Health said they had seen cases of people contracting the virus twice. 

Elon Musk has become re-infected with Covid-19 which is considered rare. Photo / Getty Images 

"While it is possible to gain immunity following infection that may last for some weeks after testing positive to Covid-19, this may not protect you from reinfection, and the immunity is likely to wane," they said, speaking to The Sydney Morning Herald. 

"It is possible to be infected with another variant or the same variant again, although it is less likely you will be infected with the same variant." 

- by Jessica Wang, news.com.au