Vaccination Against Mpox Is Effective

By Stan Deresinski, MD, FACP, FIDSA

Clinical Professor of Medicine, Stanford University

SYNOPSIS: Two-dose vaccination with Jynneos is effective in the prevention of mpox (monkeypox), but a better vaccine is desirable, particularly for use in immunocompromised individuals.

SOURCE: CHI Health Alert Network. Resurgence of mpox. Provider update. May 9, 2023. https://www.chicagohan.org/alert-detail/-/alert-details/46678186

On May 9, 2023, the Chicago Department of Public Health (CDPH) said 12 confirmed and one probable case of mpox (monkeypox) had been reported to CDPH from April 17 to May, all in symptomatic men. Of the 13 patients, nine (69%) had previously been fully vaccinated against mpox, having received two doses of the Jynneos vaccine. These cases raise the question of the efficacy of the vaccine, something that has been addressed by several recent publications.

Dalton and colleagues with the Centers for Disease Control and Prevention (CDC) reported the results of a case-control study performed in 12 U.S. jurisdictions in which 309 case patients who had developed mpox were compared to 608 matched control subjects.¹ Control patients had visited a sexual health, human immunodeficiency virus (HIV) care, or HIV pre-exposure prophylaxis (PrEP) clinic on or after Aug. 19, 2022, and had not received a diagnosis of mpox. The adjusted vaccine efficacy (VE) was 75.2% (95% confidence interval [CI] = 61.2% to 84.2%) for those who had received partial (single dose) vaccination and 85.9% (95% CI = 73.8% to 92.4%) with full vaccination (two doses). Results were similar whether the vaccine was administered subcutaneously, intradermally, or a mix of the two routes. VE after two doses was reduced in subjects with immunocompromise at 70.2% and 50.1% with complete and partial vaccination, respectively. This compares to 87.8% and 72.1%, respectively, in those who were immunocompetent.

Rosenberg and colleagues in New York state matched 252 adult males who had received a diagnosis of mpox to 255 contemporaneous control adult males without an mpox diagnosis but who had male-male sexual contact and had primary syphilis or rectal gonorrhea.² The adjusted VE of a single dose was 68.1% (95% CI = 24.9% to 86.5%) and for two doses was 88.5% (95% CI = 44.1% to 97.6%).

Deputy and colleagues used the national COSMOS database from the Epic electronic health record to perform a case control study.³ Cases (n = 2,193) were adults who had had a diagnosis of mpox while controls (n = 8,319) had a history of HIV infection or were receiving HIV PrEP. VE was 35.8% (95% CI, 22.1 to 47.1) after partial vaccination and 66.0% (95% CI, 47.4 to 78.1) for full vaccination. Among immunocompromised patients, the adjusted vaccine effectiveness was 40.8% (95% CI, 24.8 to 53.4) after partial vaccination and 76.3% (95% CI, 57.7 to 86.8) with full vaccination.

COMMENTARY

While their individual results differ to an extent, these studies clearly demonstrate the efficacy of Jynneos vaccination in the prevention of mpox. They fully agree that, while a single dose provides protection, a two-dose regimen is superior. They also unsurprisingly agree that greater VE is seen in immunocompetent than in immunocompromised individuals. In the latter group, receipt of just a single dose has a VE of as low as 35.8%. This observation is of concern since many individuals with significant risk of mpox infection often are HIV infected.

Overall, while full vaccination with Jynneos is effective, the search for an even better vaccine is desirable, especially for protection of immunodeficient individuals.

REFERENCES

Dalton AF, Diallo AO, Chard AN, et al; CDC Multijurisdictional Mpox Case-Control Study Group. Estimated effectiveness of JYNNEOS vaccine in preventing mpox: A multijurisdictional case-control study – United States, August 19, 2022-March 31, 2023. MMWR Morb Mortal Wkly Rep 2023;72:553-558.
Rosenberg ES, Dorabawila V, Hart-Malloy R, et al. Effectiveness of JYNNEOS vaccine against diagnosed mpox infection — New York, 2022. MMWR Morb Mortal Wkly Rep 2023;72:559-563.
Deputy NP, Deckert J, Chard AN, et al. Vaccine effectiveness of JYNNEOS against mpox disease in the United States. N Engl J Med 2023; May 18. doi: 10.1056/NEJMoa2215201. [Online ahead of print].