1/ Q: I hear there has been a confirmed case of SARS-CoV-2 re-infection in Hong Kong?! How worried should I be?

A: Not very.

In the words of immunologist Dr. Akiko Iwasaki, “This is no cause for alarm - this is a textbook example of how immunity should work.”
3/ How do we know this was a new infection? The genetic signature of the second infection was slightly different from the first infection, providing strong evidence for separate infections rather than a relapse of the same infection.
4/ The patient was infected with SARS-CoV-2 four months prior in Hong Kong with mild symptoms. He then tested positive upon re-entry into Hong Kong from Spain but with no symptoms.
5/ So WHY is this not cause for alarm?

• The 2nd infection was asymptomatic, so while immunity didn’t block detectable infection, it protected from disease.
• The individual had no detectable antibodies after his 1st infection, while most COVID patients DO.
6/ • The individual did produce antibodies after the second exposure, consistent with the immune system eliciting a stronger response with repeated exposures.
• This is one case out of millions, so we don’t know if this is a rare event or something that will be the norm.
7/ What questions does this raise?
1️⃣ Even with no symptoms, a re-infected person *may* be able to spread the infection to others, but the extent & duration of infectiousness compared to first infections is currently not known.
8/
2️⃣ Since herd immunity relies on immune people *not* being able to infect others, this bolsters the consensus that the only safe & effective way to achieve herd immunity is through vaccination.
9/
3️⃣ Recovered COVID-19 patients will also likely need to be vaccinated, and should also continue to take standard precautions to prevent transmission to others.

Bottom line: KEEP CALM--in science ONE case never tells the whole story.
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