Mpox Vaccines May Work Against MPXV Clade I

The U.S. Centers for Disease Control and Prevention (CDC) today announced a Health Alert Network (HAN) Health Advisory about the occurrence, geographic spread, and sexually associated human-to-human transmission of Clade I Monkeypox virus (MPXV) in the Democratic Republic of the Congo (DRC).

Since January 2023, the DRC has reported 12,569 suspected mpox cases and 581 related deaths from 22 regions.

The new HAN says cases of Clade I MPXV have not been reported in the United States as of December 7, 2023. The global outbreak of Clade II MPXV was initially reported in May 2022.

However, clinicians should be aware of the possibility of Clade I MPXV in travelers who have been in DRC. 

Third-party data indicate that the number of tourists arriving in the DRC was about 460,880 in 2021.

The CDC recently issued a Travel Health Notice (Level 2 - Practice Enhanced Precautions) for people traveling to DRC. Furthermore, there are no direct commercial passenger flights from DRC to the U.S. as of December 2023.

U.S. FDA-approved vaccines (JYNNEOS, ACAM2000) are expected to be effective for both Clade I and II MPXV infections.

Vaccination or prior MPXV infection should provide antibodies that will provide cross-protection to other orthopoxviruses, including Clade I MPXV, says the CDC.

However, clinical verification is under review.

The CDC recommends clinicians encourage vaccination for eligible patients.

Eligible patients who have only received one dose of Bavarian Nordic JYNNEOS® (MVA-BN®, IMVAMUNE®) vaccine, which is based on a live, attenuated vaccinia virus, should receive the second dose as soon as possible, regardless of the time that has elapsed since the first dose.

Mpox vaccines have limited availability in the U.S.

Furthermore, clinicians should notify their state health department if they have a patient with mpox-like symptoms and should submit lesion specimens for clade-specific testing for these patients.