A case of mpox reinfection in an HIV negative gay man without immunosuppression, has just been reported in CID, occurring six months after the first infection. 
A similar case was also reported in the BMJ earlier this year, with only four months between infections, during which time the man had also received to doses of the Jynneos vaccine. 
The first case was a 31 year old man on PrEP living in Switzerland who was first diagnosed with mpox in May 2022, at the outset of the epidemic last year. Presenting symptoms included four umbilicated penile lesions. Skin lesions and pharyngeal swabs tested PCR-positive for mpox with a cycle threshold (Ct) of 16.5 and 35.3 respectively. He also tested positive for chlamydia. Within two weeks skin lesions spontaneously resolved without complications.
On 1 December, he was diagnosed with mpox a second time and proctitis after reporting anal pain without bleeding that starting two weeks earlier, four weeks after a visit to Brazil, which still reported a very high number of diy infections. Rectal swabs tested positive PCR-positive for mpox with a Ct of 27. He also tested positive for chlamydia again. Four weeks after exposure, he had an anal fissure but no typical mpox lesions.
On 13 December, orthopoxvirus PCR was negative in the blood and urine.
Unfortunately, viral isolates were only available for the first infection. The study authors discussed the potential that the second infection was due to an immune escape mutations ot that the high viraemia associated with anal lesions might have outweight eny earlier immune response. However, the median time for mpox PRC-positivity in rectal swabs is about 8 days with a 95th upper percentile of 14 days and now cases reporting persistant viral shedding over months.
The second infection was described as mild and resolved completely.
Another case of mpox reinfection in an HIV negative man on PrEP was reported in the BMJ earlier this year.
In this case, there was ony four months between the two infections during which this person has also received two doses of the Jynneos vaccine.
One dose was given a week after the first infection in July 2022 and the second was given 10 weeks later in October (5 weeks before the second infection and 9 weeks before painful anal lesions).
Both infectionsresolved without complications.
These cases show that the hoped for sterilising immunity after an initial systemic infection is not sufficiently protective to prevent subsequent infections, even after less than six months.
By Simon Collins, HIV i-Base
Source : HIV i-Base
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