#18,441
Nearly half of outbreak case-patients in 2023 were vaccinated, and there were more cases among those who had received 2 doses of MVA-BN vaccine than among those who had received 1 dose.This unexpected result, the authors posited, may have more to do with the risk behavior by some who may feel overly `protected' by two-doses of the vaccine, rather than a `failure' of the vaccine. The JYNNEOS vaccine - which was first approved in 2019 - was never expected to be 100% protective against Mpox.
Peak immunity is expected to be reached 14 days after the second dose of JYNNEOS vaccine. The duration of immunity after one or two doses of JYNNEOS is currently unknown.
Last March, in ECCMID 2024 Study: Mpox (monkeypox) Antibodies Wane Within A Year of Vaccination) we looked at a study by researchers from Erasmus MC in Rotterdam that found:
. . . recipients of the 2-Dose JYNNEOS/ IMVANEX/ IMVAMUNE mpox vaccine who did not receive a childhood smallpox vaccination (discontinued in the 1970s) experienced substantial drops in their immune response after 12 months.
Another presentation, released at roughly the same time from Sweden (see Immune response to MPXV wanes rapidly after intradermal vaccination with MVA-BN (Jynneos)) found an even quicker loss (> 28 days) of detectable neutralizing antibodies after the second vaccination, writing:
Our findings corroborate previous data showing that intradermal MVA-BN vaccination results in neutralizing antibodies only in a proportion of vaccinees, and that a significant decline occurs already during the first months post-vaccination. Immunity after MPXV infection mounts a higher and more robust neutralizing response. In conclusion, the findings merits the study of booster doses.
We saw another study last September, in Eurosurveillance: Orthopoxvirus-specific Antibodies Wane to Undetectable Levels 1 year After MVA-BN Vaccination of At-risk Individuals, which produced similar findings.
Admittedly, levels of detectable neutralizing antibodies may not tell the full story when in comes to the duration of vaccine protection. The authors cited research into memory B cells (MBCs) which may protect against severe disease long after neutralizing antibodies have waned.
All of which brings us to a new preprint which finds - 5 to 7 months after receiving a 2nd dose of the MVA-BN Mpox vaccine - a waning and low-avidity antibody response in vaccine recipients who were never `primed' with the smallpox vaccine.
I've only reproduced the link and the abstract, so follow the link to read it in its entirety. I'll have a bit more after the break.
Aaron L. Oom, Kesi K. Wilson, Miilani Yonatan, Stephanie Rettig, Heekoung Allison Youn, Michael Tuen, Yusra Shah, Ashley L. DuMont, Hayley M. Belli, Jane R. Zucker, Jennifer B. Rosen, Ramin Sedaghat Herati, Marie I. Samanovic, Ralf Duerr, Angelica C. Kottkamp, Mark J. Mulligan, the NYC OSMI Study Groupdoi: https://doi.org/10.1101/2024.01.28.24301893
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Abstract
The 2022 global outbreak of clade IIb mpox was the first major outbreak of mpox outside of African nations. To control the outbreak, public health officials began vaccination campaigns using the third-generation orthopoxvirus vaccine MVA-BN. Prior to this outbreak, the durability of MPXV-specific immunity induced by MVA-BN was poorly understood.
In 2022, we launched the New York City Observational Study of Mpox Immunity (NYC OSMI, NCT05654883), a longitudinal study of 171 participants comprising MVA-BN vaccinees and mpox convalescent individuals. Peripheral blood sampling was performed at intervals including prior to vaccination, after one dose, and after the second dose.
MVA-BN vaccinees with and without a history of smallpox vaccination demonstrated detectable mpox virus (MPXV)-specific memory B cells at one-year post-vaccination. Additionally, MVA-BN increased MPXV neutralizing titers in smallpox vaccine-naïve vaccinees, with a comparable peak titer reached in naïve and smallpox vaccine-experienced vaccinees.
However, neutralizing titers returned to baseline within 5-7 months for naïve individuals, while remaining elevated in those with prior smallpox vaccination. Both naïve and experienced individuals generated robust, immunodominant IgG responses against MPXV H3 and A35, but naïve vaccinees’ IgG responses showed lower avidity than experienced vaccinees.
These data highlight a low avidity antibody response elicited by MVA-BN that is short-lived in naïve vaccinees. This work supports the need for long-term studies on protection induced by MVA-BN including the potential need for booster doses as well as the development of next-generation orthopoxvirus vaccines.
(SNIP)
Discussion
We report here an analysis through one year of the MPXV-specific serum antibody magnitude, specificity, and avidity, and blood MBCs following the two-dose MVA-BN vaccination regimen. The current data indicate that IgG antibodies induced by MVA-BN are limited in their durability in naïve adults.
We identified immunodominant MPXV proteins and found that the IgG response to those proteins was low avidity in naïve MVA-BN recipients in comparison to experienced MVABN recipients.
We also demonstrated that MPXV-specific MBCs are detectable in circulation in a subset of vaccinees one year after vaccination despite the limited durability of circulating MPXV-specific antibodies.(Continue . . . )
While the JYNNEOS vaccine (and potentially the TPOXX antiviral) remain important tools in our battle against the Mpox virus, neither are a `silver bullet' against the virus.
And if the vaccine's protection truly wanes after 8 to 12 months, that is something that recipients need to be aware of, so they can make informed and safer decisions going forward.
