Smallpox Vaccines: A Powerful Defense Against Monkeypox

The Link Between Smallpox Vaccines and Protection Against Monkeypox

As cases of monkeypox, specifically the clade Ib variant, continue to surge in the Democratic Republic of the Congo, researchers have been exploring the effectiveness of smallpox vaccines in providing protection against this related virus. Monkeypox and smallpox share a connection, as the vaccines used to safeguard against monkeypox were originally developed for smallpox. However, the efficacy of these vaccines against monkeypox, particularly the clade Ib variant, remains uncertain.

While there is limited good-quality research on the effectiveness of smallpox vaccines against monkeypox, recent studies have shed some light on the subject. One study focused on a specific vaccine called MVA-BN, also known as JYNNEOS, Imvanex, and Imvamune, which was widely used during the 2022 monkeypox outbreak caused by the clade IIb variant in Western countries.

Research suggests that receiving a single dose of MVA-BN can lower the risk of catching monkeypox by approximately 60%. However, it is important to note that the efficacy of MVA-BN for monkeypox can vary significantly, ranging from 36% to 86%. This wide range of efficacy could be attributed to the observational nature of the studies, which compared outcomes among individuals with different ages, locations, and health statuses.

To further investigate the effectiveness of MVA-BN, randomized control trials are currently underway among gay, bisexual, and other men who have sex with men. These trials are particularly relevant as this group constituted the majority of infections during the 2022 monkeypox outbreak in Western countries.

In the absence of complete randomized control trials, researchers have attempted to mimic such trials by leveraging existing medical data. For example, a study conducted in Canada examined over 6,000 men who were considered to be at high risk of monkeypox infection in 2022. Approximately half of the participants received a single dose of MVA-BN, while the other half did not receive any monkeypox vaccine. The two groups were matched based on factors such as age and location.

During a follow-up period of around 80 days, it was observed that 50 men in the unvaccinated group were diagnosed with monkeypox, compared to 21 in the vaccinated group. This suggests that MVA-BN reduced the risk of monkeypox by 58% with just a single dose. While this level of protection is considered good for a single dose, it is important to note that the official regimen for MVA-BN recommends two doses administered at least 28 days apart for higher efficacy.

Experts in the field, such as Adam Hacker from the Coalition for Epidemic Preparedness Innovations in London and Corine Geurts van Kessel from Erasmus MC in the Netherlands, acknowledge that two doses of MVA-BN would likely provide even greater efficacy. However, they emphasize that a single dose still offers considerable protection against monkeypox.

It is worth mentioning that the study conducted in Canada had limitations. For instance, it is unclear whether some of the older participants had been vaccinated against smallpox when it was a threat, which could have influenced their immune response to MVA-BN in 2022. Additionally, further research is needed to determine how well MVA-BN works against the clade Ib variant specifically, as most studies have focused on the clade IIb variant.

Understanding the effectiveness of smallpox vaccines, such as MVA-BN, against monkeypox is crucial in combating the ongoing outbreak and protecting vulnerable populations. While more research is needed to fully comprehend the relationship between smallpox vaccines and monkeypox protection, the current evidence suggests that a single dose of MVA-BN can provide significant defense against this related virus.

The Impact of Smallpox Vaccines on Monkeypox Protection

The effectiveness of smallpox vaccines, particularly MVA-BN, in providing protection against monkeypox has significant implications for controlling the ongoing outbreak and safeguarding vulnerable populations. The observed effect of receiving a single dose of MVA-BN is a notable reduction in the risk of contracting monkeypox.

Studies have shown that a single dose of MVA-BN can lower the risk of catching monkeypox by approximately 60%. This level of protection is considered significant, considering the potential severity of the disease and the absence of specific monkeypox vaccines. The reduction in the number of diagnosed cases among vaccinated individuals compared to the unvaccinated group further supports the effectiveness of MVA-BN.

While the official regimen for MVA-BN recommends two doses administered at least 28 days apart for higher efficacy, the observed effect of a single dose in reducing the risk of monkeypox by 58% is encouraging. This finding suggests that even with a single dose, MVA-BN provides a considerable level of protection against monkeypox.

Experts in the field, such as Adam Hacker and Corine Geurts van Kessel, acknowledge that two doses of MVA-BN would likely offer even greater efficacy. However, the observed effect of a single dose is significant enough to support the use of MVA-BN in controlling the spread of monkeypox, particularly in high-risk populations.

Understanding the effectiveness of smallpox vaccines against monkeypox is crucial for public health interventions and outbreak management. The effect of MVA-BN in reducing the risk of monkeypox highlights the potential of repurposing existing vaccines to combat related viral diseases.

Further research is needed to explore the specific effects of MVA-BN against the clade Ib variant, which is currently driving the surge in monkeypox cases in the Democratic Republic of the Congo. While studies have primarily focused on the clade IIb variant, experts anticipate that MVA-BN will exhibit at least some effectiveness against the clade Ib variant as well.

Assessing the overall efficacy of MVA-BN in terms of reducing the severity of illness once infected with monkeypox would provide valuable insights into its broader impact. This information would help in evaluating the vaccine’s effectiveness beyond just preventing infection and understanding its potential role in mitigating the severity of the disease.

In conclusion, the observed effect of a single dose of MVA-BN in reducing the risk of monkeypox by 58% demonstrates the significant impact of smallpox vaccines on providing protection against this related virus. While further research is needed to fully comprehend the relationship between smallpox vaccines and monkeypox protection, the current evidence supports the use of MVA-BN in controlling the ongoing outbreak and protecting vulnerable populations.