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Mingda Xu, Caifen Liu, Zhanwei Du, Yuan Bai, Zhen Wang, Chao Gao, Real-world effectiveness of monkeypox vaccines: a systematic review, Journal of Travel Medicine, Volume 30, Issue 5, July 2023, taad048, https://doi.org/10.1093/jtm/taad048
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Mpox (monkeypox) virus is a deoxyribonucleic acid virus in the orthopoxvirus genus, which was first identified amongst humans in the Democratic Republic of the Congo in 1970. In May 2022, a series of mpox cases were identified in non-endemic countries and has rapidly spread worldwide. On 23 July 2022, the World Health Organization declared the mpox outbreak a Public Health Emergency of International Concern. As of 1 February 2023, 85 531 cases and 91 deaths had been reported in over 110 locations. The urgent need to mitigate mpox transmission, especially for populations at risk,1,2 has surged the accelerating development of mpox vaccines and treatments. The first-generation vaccine (e.g. Dryvax) is no longer available since the cessation of smallpox vaccination after eradication in 1980. Then, the second-generation vaccine (ACAM2000) was approved by US Food and Drug Administration (FDA) against orthopoxvirus in August 2007. The third-generation smallpox vaccines like MVA-BN (Modified Vaccinia Ankara-Bavarian Nordic, also known as JYNNEOS and IMVANEX) are expected to be the critical factors that can significantly convert the mpox prevention strategies. However, the efficacy of current vaccines against mpox has been inferred from animal and immunogenicity studies but has barely been demonstrated in human clinical trials.3 Understanding the effectiveness amongst humans can inform public health for future preparedness of mpox prophylaxis. We conducted a systematic literature review to evaluate the real-world effectiveness of mpox vaccines.
We identified 249 articles by searching PubMed, 123 by Web of Science and seven studies from expert recommendation and retrieved 192 related preprints from medRxiv and bioRxiv as of 3 March 2023. We screened 524 studies and included nine in this review that met the criteria, as shown in Figure S1. The results of the effectiveness study for the third-generation vaccine (MVA-BN) are summarized in Table 1, whilst those for the first-generation vaccine are presented in Table S1.
| Source . | Vaccinea . | Study period . | Location . | Vaccination strategyb . | Population . | Dosec . | VEd . | Estimated 95% CI . |
|---|---|---|---|---|---|---|---|---|
| Chard A et al. 20234 | MVA-BN (Third generation) | 22 May–24 August, 2022 | USA (New York City) | PEPV | Individuals aged ≥18 years | 1 | 79% | 46–94% |
| Chard A et al. 20234 | MVA-BN (Third generation) | 24 July–31 October, 2022 | USA (New York State) | PPV | Males aged ≥18 years | 1 | 68% | 25–86% |
| 2 | 89% | 44–98% | ||||||
| Chard A et al. 20234 | MVA-BN (Third generation) | / | USA | PPV | Males aged 18–49 years | 2 | 76%* | 48–89%* |
| Payne AB et al. 20225 | MVA-BN (Third generation) | 31 July–1 October, 2022 | The U.S. | PPV | Males aged 18–49 years | 1 | 87% | 83–89% |
| 2 | 90% | 86–92% | ||||||
| Payne AB et al. 20226 | MVA-BN (Third generation) | 31 July–3 September, 2022 | USA | PPV | Males aged 18–49 years | 1 | 93% | 80–98% |
| Arbel R et al. 20227 | MVA-BN (Third generation) | 31 July–12 September, 2022 | Israel | PPV | Males aged 18–42 years | 1 | 79% | 24–94% |
| Bertran M et al. 20238 | MVA-BN (Third generation) | 4 July–9 October, 2022 | England | PPV | Males aged <50 years | 1 | 78% | 54–89% |
| Sagy YW et al. 20239 | MVA-BN (Third generation) | 31 July–25 December, 2022 | Israel | PPV | Males aged 18–42 years | 1 | 86%* | 59–95%* |
| Source . | Vaccinea . | Study period . | Location . | Vaccination strategyb . | Population . | Dosec . | VEd . | Estimated 95% CI . |
|---|---|---|---|---|---|---|---|---|
| Chard A et al. 20234 | MVA-BN (Third generation) | 22 May–24 August, 2022 | USA (New York City) | PEPV | Individuals aged ≥18 years | 1 | 79% | 46–94% |
| Chard A et al. 20234 | MVA-BN (Third generation) | 24 July–31 October, 2022 | USA (New York State) | PPV | Males aged ≥18 years | 1 | 68% | 25–86% |
| 2 | 89% | 44–98% | ||||||
| Chard A et al. 20234 | MVA-BN (Third generation) | / | USA | PPV | Males aged 18–49 years | 2 | 76%* | 48–89%* |
| Payne AB et al. 20225 | MVA-BN (Third generation) | 31 July–1 October, 2022 | The U.S. | PPV | Males aged 18–49 years | 1 | 87% | 83–89% |
| 2 | 90% | 86–92% | ||||||
| Payne AB et al. 20226 | MVA-BN (Third generation) | 31 July–3 September, 2022 | USA | PPV | Males aged 18–49 years | 1 | 93% | 80–98% |
| Arbel R et al. 20227 | MVA-BN (Third generation) | 31 July–12 September, 2022 | Israel | PPV | Males aged 18–42 years | 1 | 79% | 24–94% |
| Bertran M et al. 20238 | MVA-BN (Third generation) | 4 July–9 October, 2022 | England | PPV | Males aged <50 years | 1 | 78% | 54–89% |
| Sagy YW et al. 20239 | MVA-BN (Third generation) | 31 July–25 December, 2022 | Israel | PPV | Males aged 18–42 years | 1 | 86%* | 59–95%* |
aMVA-BN: also known as IMVAMUNE®, JYNNEOS and IMVANEX.
bPEPV: Post-exposure preventive vaccination is recommended for contacts of known cases within 4 days of first exposure (and up to 14 days in the absence of symptoms), also recommended subcutaneous vaccination of persons with known or presumed exposure to mpox; PPV: Primary preventive (pre-exposure) vaccination for persons in high-risk. Considering that PEPV includes ring vaccination strategy and PPV is a targeted vaccination strategy.
cMVA-BN is administered subcutaneously as two doses separated by 4 weeks (one dose at week 0 and a second dose at week 4) for primary vaccines (individuals who have never been vaccinated against smallpox or do not recall receiving a smallpox vaccination in the past.)
dVE: Vaccine Effectiveness; * in VE represents the Adjusted VE for age, race/ethnicity, social vulnerability index and immunocompromising conditions.
| Source . | Vaccinea . | Study period . | Location . | Vaccination strategyb . | Population . | Dosec . | VEd . | Estimated 95% CI . |
|---|---|---|---|---|---|---|---|---|
| Chard A et al. 20234 | MVA-BN (Third generation) | 22 May–24 August, 2022 | USA (New York City) | PEPV | Individuals aged ≥18 years | 1 | 79% | 46–94% |
| Chard A et al. 20234 | MVA-BN (Third generation) | 24 July–31 October, 2022 | USA (New York State) | PPV | Males aged ≥18 years | 1 | 68% | 25–86% |
| 2 | 89% | 44–98% | ||||||
| Chard A et al. 20234 | MVA-BN (Third generation) | / | USA | PPV | Males aged 18–49 years | 2 | 76%* | 48–89%* |
| Payne AB et al. 20225 | MVA-BN (Third generation) | 31 July–1 October, 2022 | The U.S. | PPV | Males aged 18–49 years | 1 | 87% | 83–89% |
| 2 | 90% | 86–92% | ||||||
| Payne AB et al. 20226 | MVA-BN (Third generation) | 31 July–3 September, 2022 | USA | PPV | Males aged 18–49 years | 1 | 93% | 80–98% |
| Arbel R et al. 20227 | MVA-BN (Third generation) | 31 July–12 September, 2022 | Israel | PPV | Males aged 18–42 years | 1 | 79% | 24–94% |
| Bertran M et al. 20238 | MVA-BN (Third generation) | 4 July–9 October, 2022 | England | PPV | Males aged <50 years | 1 | 78% | 54–89% |
| Sagy YW et al. 20239 | MVA-BN (Third generation) | 31 July–25 December, 2022 | Israel | PPV | Males aged 18–42 years | 1 | 86%* | 59–95%* |
| Source . | Vaccinea . | Study period . | Location . | Vaccination strategyb . | Population . | Dosec . | VEd . | Estimated 95% CI . |
|---|---|---|---|---|---|---|---|---|
| Chard A et al. 20234 | MVA-BN (Third generation) | 22 May–24 August, 2022 | USA (New York City) | PEPV | Individuals aged ≥18 years | 1 | 79% | 46–94% |
| Chard A et al. 20234 | MVA-BN (Third generation) | 24 July–31 October, 2022 | USA (New York State) | PPV | Males aged ≥18 years | 1 | 68% | 25–86% |
| 2 | 89% | 44–98% | ||||||
| Chard A et al. 20234 | MVA-BN (Third generation) | / | USA | PPV | Males aged 18–49 years | 2 | 76%* | 48–89%* |
| Payne AB et al. 20225 | MVA-BN (Third generation) | 31 July–1 October, 2022 | The U.S. | PPV | Males aged 18–49 years | 1 | 87% | 83–89% |
| 2 | 90% | 86–92% | ||||||
| Payne AB et al. 20226 | MVA-BN (Third generation) | 31 July–3 September, 2022 | USA | PPV | Males aged 18–49 years | 1 | 93% | 80–98% |
| Arbel R et al. 20227 | MVA-BN (Third generation) | 31 July–12 September, 2022 | Israel | PPV | Males aged 18–42 years | 1 | 79% | 24–94% |
| Bertran M et al. 20238 | MVA-BN (Third generation) | 4 July–9 October, 2022 | England | PPV | Males aged <50 years | 1 | 78% | 54–89% |
| Sagy YW et al. 20239 | MVA-BN (Third generation) | 31 July–25 December, 2022 | Israel | PPV | Males aged 18–42 years | 1 | 86%* | 59–95%* |
aMVA-BN: also known as IMVAMUNE®, JYNNEOS and IMVANEX.
bPEPV: Post-exposure preventive vaccination is recommended for contacts of known cases within 4 days of first exposure (and up to 14 days in the absence of symptoms), also recommended subcutaneous vaccination of persons with known or presumed exposure to mpox; PPV: Primary preventive (pre-exposure) vaccination for persons in high-risk. Considering that PEPV includes ring vaccination strategy and PPV is a targeted vaccination strategy.
cMVA-BN is administered subcutaneously as two doses separated by 4 weeks (one dose at week 0 and a second dose at week 4) for primary vaccines (individuals who have never been vaccinated against smallpox or do not recall receiving a smallpox vaccination in the past.)
dVE: Vaccine Effectiveness; * in VE represents the Adjusted VE for age, race/ethnicity, social vulnerability index and immunocompromising conditions.
During the 2022 mpox outbreak, we estimated that the vaccine effectiveness of MVA-BN against mpox was 87% [95% confidence interval (CI): 84–90%] for one-dose vaccination and 89% (95% CI: 78–100%) for two-dose vaccination, based on pooled estimates (Figure S2). The results showed that the incidence of mpox was significantly lower in the vaccinated group than in the unvaccinated group. According to previous studies, the first-generation smallpox vaccine had an effectiveness of 58% (95% CI: 17–78%) in preventing severe cases of mpox disease (Table S1).
Our study has some limitations, including significant variations in the included studies. The reported results are real-world vaccine effectiveness against mpox, which may vary over studies due to factors (e.g. estimation methods, sample size).
In summary, the results from the included studies demonstrated the encouraging effectiveness of the mpox vaccines being widely used. Vaccines, antivirals and other treatments should be implemented promptly and monitoring of the virus must be ongoing. Additionally, vaccination strategy such as targeted and ring vaccination are essential components of the response to effectively contain mpox disease.10 Considering the potential mutations, side effects and breakthrough infections, it is recommended to develop a next-generation vaccine that is more effective and safer for mpox outbreaks.
Funding
We acknowledge the financial support from the National Key R&D of China (No. 2022YFE0112300), National Natural Science Foundation of China (Nos. 61976181, 62261136549, U22B2036), Technological Innovation Team of Shaanxi Province (No. 2020TD-013).
Authors’ contributions
Mingda Xu and Caifen Liu (Literature search and created the tables and figures), Mingda Xu and Zhanwei Du (Conducted analyses, interpreted results, wrote and revised the manuscript) and Yuan Bai, Zhen Wang and Chao Gao (Interpreted results and revised the manuscript).
Conflict of interest
The authors declare no competing interests.
Data availability
The data underlying this article and these programmes will be shared on reasonable request with the corresponding author.
References
Chard A.
Bertran M, Andrews N, Davison C et al. . Effectiveness of one dose of MVA-BN smallpox vaccine against mpox in England using the case-coverage method: an observational study.
