Mpox vax holds up against severe infection

Individuals who have received mpox vaccination or have been previously exposed to mpox infection, which is used to be called monkeypox, appear to be better protected against severe disease from a subsequent infection, as shown in a study.

Data on mpox infections in 37 men who have sex with men (median age 36 years) showed that the 30 cases of infection that occurred postvaccination were not severe, with few lesions, less mucosal involvement, and minimal painkiller requirements. However, there were two individuals who were given an mpox-specific antiviral therapy, specifically a 14-day course of tecovirimat, due to swelling and pain from an oropharyngeal lesion in one and due to involvement of the neck necessitating hospitalization in the other. [Lancet Infect Dis 2023;doi:10.1016/S1473-3099(23)00492-9]

Meanwhile, the eight cases of repeat mpox infections were characterized by a shorter disease course, with less mucosal disease upon reinfection than what was seen during the initial infection.

Overall, none of the individuals died and contracted bacterial superinfections. All of them were managed in the ambulatory clinic with one hospital admission for a necrotizing neck lesion.

“Clinical presentation of both repeat infections and infections after vaccination appeared to differ from the 2022 case literature on initial infections. The infections from the 2022 case literature had been characterized by evolution of painful pseudopustules at the anogenital areas with mucosal involvement in around 40 percent of cases, as well as frequent debilitating oral lesions and [common requirement of] antibiotic treatment for bacterial superinfection,” according to the investigators. [N Engl J Med 2022;387:679-691; Lancet 2023;401:939-949; MMWR Morb Mortal Wkly Rep 2022;71:1610-1615]

“In infections postvaccination, solitary lesions were the most common presentation in our case series, whereas in the 2022 global case series, only 10 percent presented as solitary lesion. The anogenital area remained the most commonly involved site, although mucosal lesions occurred less commonly than described in the 2022 case literature,” they added. [N Engl J Med 2022;387:679-691]

Looking at the Mpox Severity Score System (SSS), the median score was 5 (range 3-11) among individuals with postvaccination infections. Among those with repeat mpox infections, on the other hand, the median score decreased from 7 at the initial infection to 5.5 at the second infection.

The investigators noted that individuals who contracted mpox infection after vaccination had numerically lower scores with respect to the extent of nongenital involvement, number of mucosal areas affected, and analgesia requirement compared with those who had repeat infections.

Push for mpox vaccinations

The epidemiology of the infections presented in this study is consistent with that of the published series and cohorts of primary mpox infection early in the 2022 outbreak, with the infections all occurring in sexually active gay and bisexual men who have sex with men with multiple sexual partners. Condomless sexual contact remained the primary route of transmission, with a third of the sample population having concomitant sexually transmitted infections diagnosed at the time of their mpox infection.

“These findings support the literature, signalling that vaccinations might reduce duration and severity. Efforts to revitalize mpox vaccination campaigns continue in North America and Europe because sustained transmission in humans coupled with gaps in vaccine coverage, especially in racially minoritized communities, creates vulnerability for an mpox resurgence,” the investigators said. [MMWR Morb Mortal Wkly Rep 2023;72:696-698; MMWR Morb Mortal Wkly Rep 2022;71:1610-1615; https://www.cdc.gov/poxvirus/mpox/response/2022/risk-assessment-of-resurgence.html]

They also stressed the importance of developing consistent and clear interventions with the aim of improving vaccination uptake, as well as increasing knowledge regarding vaccine effectiveness in preventing infection.

“Above all, ensuring equity of access to vaccines and treatments, specifically to geographical areas historically affected by mpox, must be prioritized if we aim to end this global outbreak and ensure elimination of human-to-human mpox transmission,” the investigators pointed out.