U.S. NIAID and Harvard Study Reveals Antibodies from Jynneos Mpox Vaccine Wane After 6 to 12 Months

Medical News: A recent study led by researchers from the U.S. National Institute of Allergy and Infectious Diseases (NIAID) and Harvard University has uncovered significant findings regarding the durability of the immune response from the Jynneos Mpox vaccine. The study revealed that antibodies developed from the vaccine, also known as the Modified Vaccinia Ankara - Bavarian Nordic (MVA-BN), tend to diminish between six to twelve months after vaccination. This Medical News report dives deeper into these important findings, exploring what they mean for long-term protection against Mpox.


U.S. NIAID and Harvard Study Reveals Antibodies from Jynneos Mpox Vaccine Wane After 6 to 12 Months

The Importance of Vaccine Durability
The Jynneos Mpox vaccine, produced by Bavarian Nordic, was a critical tool during the 2022 outbreak of the Mpox virus, previously known as monkeypox. The Centers for Disease Control and Prevention (CDC) had recommended its use, and it became a primary defense strategy during the pandemic. However, with limited vaccine supplies, the dosage was adjusted, moving from a standard 0.5 mL subcutaneous dose to a smaller 0.1 mL intradermal dose. Although both dosages were shown to generate a similar immune response, researchers were interested in determining the long-term effectiveness of these doses, especially as the World Health Organization declared a public health emergency regarding the Mpox outbreak in the Democratic Republic of Congo in August 2024.
 
The goal of this study was to evaluate the durability of immune protection in people vaccinated with Jynneos in 2022. Specifically, the study sought to measure antibody levels and overall immunity over a one-year period, assessing whether these protective elements remained strong or if they started to wane.
 
Methodology of the Study
The research, conducted between August 2022 and October 2023, involved 45 participants from Beth Israel Deaconess Medical Center, a Harvard Medical School affiliate, and NIAID in Bethesda, Maryland. These individuals either received one or two doses of the Jynneos vaccine or had a confirmed diagnosis of Mpox during the 2022 outbreak. Serum specimens were collected from these participants at regular intervals: baseline, three weeks after vaccination (considered peak immunity), and then at three, six, nine, and twelve months.
 
Antibody levels were measured against several Mpox antigens known to provide protection in animal models. Additionally, T-cell responses, which are another critical aspect of immune defense, were also evaluated. The results from these measurements formed the basis of the study’s conclusions about the durability of immunity from the vaccine.
 
Key Findings: Waning Immunity
One of the most striking revelations from this study was the clear decline in antibody levels over time. In participants who received two doses of the vaccine, antibody levels peaked three weeks after the final dose but showed a marked reduction by the twelve-month mark. Specifically, antibody respon ses to key Mpox antigens - M1R, B6R, A35R, A29L, and H3L - dropped considerably. For instance, antibodies to the M1R antigen, which started at a baseline of 28, peaked at 112 three weeks after vaccination but then dropped to just 38 at the twelve-month mark.
 
A similar pattern was observed in participants who received only one dose. Their antibody levels also peaked at three weeks but demonstrated a more significant decline, reaching near-baseline levels by twelve months.
 
Additionally, the study found that serum neutralizing antibodies, which are crucial for blocking virus infection, were minimal at three months for both one-dose and two-dose recipients. In contrast, participants who had naturally contracted the virus exhibited much higher and more sustained levels of these neutralizing antibodies, suggesting that natural infection may provide more robust long-term immunity.
 
T-Cell Responses: A Low Contribution to Long-Term Immunity
T-cells are another important part of the immune system, capable of identifying and destroying virus-infected cells. However, this study found that both CD4+ and CD8+ T-cell responses were low at nine months post-vaccination. In participants who received either one or two doses, these responses were minimal, indicating that the vaccine's ability to stimulate long-lasting cellular immunity might be limited.
 
Implications of the Study
The study's findings have raised important questions about the long-term effectiveness of the Jynneos Mpox vaccine. Given the waning antibody levels, especially after just six to twelve months, there are concerns that individuals who were vaccinated during the 2022 outbreak may now have reduced protection against Mpox. This could increase their risk of reinfection if they encounter the virus again.
 
The research also highlights the need for potential booster doses to maintain a sufficient level of immunity. Given that natural infection seems to provide more lasting immunity, additional vaccine doses might be necessary to mimic the immune response seen in those who have contracted Mpox. This need for booster shots is particularly important for individuals who are at higher risk of exposure to the virus, such as healthcare workers and those living in areas with active outbreaks.
 
Limitations of the Study
While the study provides valuable insights, the authors caution that its conclusions are limited by certain factors. For example, the study had a relatively small sample size, and the participants were not randomly selected. This could mean that the findings might not be fully representative of the broader population. Additionally, the observational nature of the study means that there is still much to learn about how well the vaccine performs over time in different demographic groups and regions.
 
Larger-scale studies with more diverse participant groups will be needed to confirm these findings and to better understand how the vaccine performs over longer periods and in various settings.
 
Conclusion
The research conducted by NIAID and Harvard University provides critical information about the Jynneos Mpox vaccine’s effectiveness over time. The evidence that antibodies wane within six to twelve months suggests that individuals vaccinated in 2022 may need booster shots to maintain adequate protection. This information is particularly relevant as Mpox continues to pose a global health threat, especially in regions with ongoing outbreaks. Furthermore, the study underscores the importance of continued monitoring of vaccine efficacy and the need for larger studies to confirm these findings.
 
The study findings were published in the peer-reviewed Journal of the American Medical Association (JAMA).
https://jamanetwork.com/journals/jama/fullarticle/2824688
 
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