Mpox update: recent publications (2023)

Simon Collins, HIV i-Base

Luckily, throughout 2023, mpox remained at low levels in the UK. Less than a handful of cases were reported for most weeks, generally at London clinics and often linked to recent international travel.

Hopefully this trend will optimistically continue next year, although it is difficult to predict future risks as the durability of vaccine protection is not yet understood.

The following papers were published recently and may be of interest.

Low CD4 vs detectable viral load as predictors of severe mpox

A review from Brazil of approximately 400 cases reported at a single clinic from June to December 2022, half who were living with HIV, highlighted very low CD4 count as the predominant risk for more severe symptoms. Both deaths were in people with a CD4 count <50 cells/mm3. [1]

Although low CD4 count was a significant predictor of worse mpox, a similar size cohort from the US reported that only detectable viral load >200 copies/mL was significant in multivariate analysis with twice the odds compared to those who were undetectable (2.10 [95% CI: 1.00 to 4.39]). [2]

Another paper in JID reported severe and prolonged mpox in three people with advanced HIV and CD4 counts of 127, 7 and <20. All cases report multiple detailed complications with mpox persisting for many months, even with tecovirimat. The person with the CD4 count of 7 cells/mm3 died on day 202 still showing mpox antigen in lung and skin tissue. [3]

Complications of mpox

A case report of inguinal lymphadenitis several weeks after mpox had resolved emphasised the potential for sexually transmitted co-infections and bacterial superinfections to complicate mpox, and that viral DNA continued to persist in affected sites after initial symptoms had resolved. [4]

Complicated mpox cases that were unresponsive to tecovirimat were reported in a US cohort from Los Angeles. The cohort included more than 1580 cases, of which approximately half were HIV positive and 60 had a CD4 count >200 cells/mm3. Overall, 134 were complicated (8.5%), including 8 cases that were not responsive to tecovirimat, all with a CD4 count >200 cells/mm3. At the time of reporting, only three people had fully resolved mpox and the single death was in a 30-year-old transgender women who presented with a CD4 count <35 cells/mm3 and a viral load >130,000 copies/mL. [5]

Another study from Atlanta reported mpox viral dynamics in different body sites (from throat, skin and anogenital tissue) in ten HIV positive people with mpox infection, also looking at markers of infectivity. [6]

Vaccine non-responders: breakthrough infection

An interesting case report was of a breakthrough mpox infection in someone who was a non-responder to the mpox vaccine. [7]

The 39-year-old gay man was on PrEP, and also on high-dose prednisolone for four months with other drugs to manage severe asthma following SARS-CoV-2 infection.

He was one of ten other participants in a small mpox vaccine study (12% n=10/85) who did not show detectable antibodies six months after the vaccine (antibody titre <1/10) and who was categorised as a non-responder. The steroid treatment at the time of vaccination was suggested as a possible explanation of the non-response.

The authors report that antibody responses generally remain higher in people who previously experienced mpox compared to vaccination, but that breakthrough infections have been reported in individuals from both groups.

They also suggest that antibody response testing might be clinically useful to identify individual risk for mpox in the future.

The November issue of Lancet Infectious Diseases included a review of other breakthrough infectious, generally within two weeks of receiving a vaccine, and also noting lower immune responses in people living with, compared to without HIV. [8]


  1. Silva MST et al, Mpox severity and associated hospitalizations among people with HIV and related immunosuppression in Brazil. AIDS38(1):p 105-113, January 01, 2024. DOI: 10.1097/QAD.0000000000003748
  2. Aldred B et al. Associations between HIV and Severe Mpox in an Atlanta Cohort,The Journal of Infectious Diseases, 2023; jiad505.
  3. O’Shea J et al. Prolonged mpox disease in people with advanced HIV: characterization of mpox skin lesions. Journal of Infectious Diseases, jiad532, (29 November 2023).
  4. Phillips MC et al. Inguinal lymphadenitis after mpox infection: A case report. Ann Int Med. 21 November 2023).
  5. Karan A et al. Surveillance of complicated mpox cases unresponsive to oral tecovirimat in Los Angeles County, 2022, The Journal of Infectious Diseases, 2023; jiad517. (23 November 2023).
  6. Damhorst GL et al, Multisite mpox infection and viral dynamics among persons with HIV in metro-Atlanta. The Journal of Infectious Diseases, jiad530, (29 November 2023).
  7. Bottanelli M et al. A case of breakthrough mpox infection in an individual non-responder to MVA-BN vaccination: Lancet Inf Dis, doi: 10.1016/S1473-3099(23)00741-7. (7 December 2023).
  8. Taha AM et al. Mpox breakthrough infections: concerns and actions. Lancet Inf Dis, 23(11); p1216-1218. DOI: (6 September 2023).



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