Acceptance and timeliness of post-exposure vaccination against mpox in high-risk contacts, Amsterdam, the Netherlands, May-July 2022

Vaccine effectiveness of 3rd generation mpox vaccines against mpox and disease severity: A systematic review and meta-analysis

INTRODUCTION

Before the global mpox outbreak which began in 2022, the real-world vaccine effectiveness (VE) of mpox vaccines was unknown. We quantified the VE in the global population of 3rd generation or later mpox vaccines (MVA-BN, LC16m8, OrthopoxVac) compared with unvaccinated or other vaccinated states for infection, hospitalization and death. VE was stratified by 1-dose and 2-doses and post-exposure prophylaxis (PEP).

METHODS

Studies were included if they measured vaccine efficacy or effectiveness in humans. Animal studies and immunogenicity studies were excluded. MEDLINE, Web of Science, Google Scholar, Embase, MedRxiv and grey literature were searched from January 1st, 1970, with the last search run on November 3, 2023 (Prospero, CRD42022345240). Risk of publication bias was assessed via funnel plots and Egger's test, and study quality via Newcastle-Ottawa scales.

RESULTS

A total of 11,892 records were identified via primary search, 3,223 via citation chasing. Thirty-three studies were identified of 3rd generation vaccines, 32 of which were MVA-BN. Two additional studies were re-analysis of existing data. Most of these studies were focused on gay, bisexual, or other men who have sex with men between the ages of 18-49 in May to October of 2022. VE of 1 dose of MVA-BN was 76% (95%CI 64-88%) from twelve studies. VE of 2 doses was 82% (95%CI 72-92%) from six studies. VE of MVA-BN PEP against mpox was 20% (95%CI -24-65%) from seven studies. All VE are calculated from random effects estimates. 18/33(55%) studies were rated as poor, 3/33(9%) as fair and 12/33(36%) as good. Studies included in the meta-analysis had higher quality: 11/16 (69%) were rated as good quality.

CONCLUSION

Both 1 and 2 doses of MVA-BN are highly effective at preventing mpox. Effectiveness estimates, specifically of PEP are limited by immortal time bias, predominant mode of mpox transmission, and real-world vaccine timing of administration.

Global prevalence and correlates of mpox vaccine acceptance and uptake: a systematic review and meta-analysis

BACKGROUND

Vaccination has been recommended as one of the most potent ways of controlling the mpox (formerly, monkeypox) outbreak, particularly among high-risk groups. Here, we evaluated the prevalence of mpox vaccine acceptance and uptake globally.

METHODS

We searched multiple databases for peer-reviewed studies published in English from May 2022 to 25th November 2023 that evaluated mpox vaccine acceptance and/or uptake. We fit a random-effects model meta-analysis to calculate the pooled mpox vaccine acceptance and uptake rates, with their 95% confidence intervals (CI) across population outcomes. We performed subgroup analyses among the six World Health Organization (WHO) regions (Africa [AFR], Region of the Americas [AMR], South-East Asia Region [SEAR], European Region [EUR], Eastern Mediterranean Region [EMR], and the Western Pacific Region [WPR]), as well as among select population subgroups.

RESULTS

Of the 2531 studies screened, 61 studies, with a cumulative sample size of 263,857 participants from 87 countries were eligible for inclusion. The overall vaccine acceptance and uptake rates were 59.7% and 30.9% globally. Acceptance and uptake rates among the LGBTQI+ community were 73.6% vs 39.8% globally, 60.9% vs. 37.1% in AMR, 80.9% vs. 50.0% in EUR, and 75.2% vs. 33.5% in WPR. Among PLHIV, vaccine acceptance and uptake rates were 66.4% vs. 35.7% globally, 64.0% vs. 33.9% in AMR, 65.1% vs. 27.0% in EUR, and 69.5% vs. 46.6% in WPR. Among healthcare workers, vaccination intention was 51.0% globally.

CONCLUSIONS

Tailored interventions are needed to bolster confidence in the mpox vaccine, maximize vaccine uptake, and increase vaccine access to close the gaps between acceptance and uptake especially among key populations residing in regions with low rates of acceptance and uptake.

Factors potentially contributing to the decline of the mpox outbreak in the Netherlands, 2022 and 2023

BackgroundIn 2022 and 2023, a global outbreak of mpox affected mostly gay, bisexual and other men having sex with men (GBMSM). Outbreak control in the Netherlands included isolation, quarantine, post-exposure prophylaxis vaccination and primary preventive vaccination (PPV).AimWe describe the course of the outbreak, the vaccination programme, vaccine effectiveness (VE) of full vaccination against symptomatic disease, and trends in behaviour to generate hypotheses about factors that influenced the outbreak's decline.MethodsIn this observational study, we collected data from public health services on notified cases, number of PPV invitations and PPV doses administered. We calculated PPV uptake and coverage. Trends in behavioural data of GBMSM visiting sexual health centres were analysed for all consultations in 2022. We estimated VE using the screening method.ResultsUntil 31 December 2023, 1,294 mpox cases were reported. The outbreak peaked in early July 2022 and then declined sharply. PPV started on 25 July 2022; in total 29,851 doses were administered, 45.8% received at least one dose, 35.4% were fully vaccinated. The estimated VE was 68.2% (95% CI 4.3-89.5%). We did not observe an evident decrease in high-risk behaviour.DiscussionIt is unlikely that PPV was a driver of the outbreak's decline, as incidence started to decline well before the start of the PPV programme. The possible impact of behavioural change could not be demonstrated with the available indicators, however, the data had limitations, hampering interpretation. We hypothesise that infection-induced immunity in high-risk groups was an important factor explaining the decline.

JYNNEOS™ effectiveness as post-exposure prophylaxis against mpox: Challenges using real-world outbreak data

BACKGROUND

JYNNEOSTM vaccine has been used as post-exposure prophylaxis (PEP) during a mpox outbreak in New York City (NYC). Data on effectiveness are limited.

METHODS

Effectiveness of a single dose of JYNNEOSTM vaccine administered subcutaneously ≤ 14 days as PEP for preventing mpox disease was assessed among individuals exposed to case-patients from May 22, 2022-August 24, 2022. Individuals were evaluated for mpox through 21 days post-exposure. An observational study was conducted emulating a sequence of nested "target" randomized trials starting each day after exposure. Results were adjusted for exposure risk and race/ethnicity. Analyses were conducted separately based on last (PEPL) and first (PEPF) exposure date. We evaluated the potential to overestimate PEP effectiveness when using conventional analytic methods due to exposed individuals developing illness before they can obtain PEP (immortal time bias) compared to the target trial.

RESULTS

Median time from last exposure to symptom onset (incubation period) among cases that did not receive PEPL was 7 days (range 1-16). Time to PEPL receipt was 7 days (range 0-14). Among 549 individuals, adjusted PEPL and PEPF effectiveness was 19 % (95 % Confidence Interval [CI], -54 % to 57 %) and -7% (95 % CI, -144 % to 53 %) using the target trial emulation, respectively, and 78 % (95 % CI, 50 % to 91 %) and 73 % (95 % CI, 31 % to 91 %) using conventional analysis.

CONCLUSIONS

Determining PEP effectiveness using real-world data during an outbreak is challenging. Time to PEP in NYC coupled with the observed incubation period resulted in overestimated PEP effectiveness using a conventional method. The target trial emulation, while yielding wide confidence intervals due to small sample size, avoided immortal time bias. While results from these evaluations cannot be used as reliable estimates of PEP effectiveness, we present important methodologic considerations for future evaluations.