Are Mpox Vaccine Boosters Recommended

As of April 2024, it remains unclear how long the immune response from mpox vaccination lasts and whether prior smallpox vaccination impacts it.

A recent study assessed the level of antibodies one year after vaccination with JYNNEOS® (MVA-BN®, IMVAMUNE®).

Announced at the European Congress of Clinical Microbiology and Infectious Diseases on March 30, 2024, this abstract indicates that people who had received smallpox vaccination during childhood and had pre-existing immunity showed high levels of antibodies generated by mpox vaccine, which remained high in almost all cases.

The authors suggested in a press release that the decrease in antibodies over time following MVA-BN vaccination may be attributable to its composition.

They stated, "The first and second-generation smallpox vaccines contained replication-competent vaccinia virus. MVA-BN is based on non-replicating virus, which may impact the strength and duration of the immune response, with the advantage of a low risk of side effects."

They add, "Regarding the potential necessity for a booster, it is premature to draw such conclusions. It is unclear how waning antibody levels relate to protection. Immunity also involves other elements, such as T-cell responses."

"Comprehensive clinical monitoring over time, which connects infection rates with antibody levels, is required to make informed decisions about booster vaccination protocols."

Bavarian Nordic A/S, the producer of JYNNEOS, the only FDA-approved mpox vaccine, recently announced that the mpox vaccine is commercially available in the U.S. at clinics and pharmacies.

The standard U.S. FDA regimen for JYNNEOS involves a subcutaneous administration with two injections of 0.5mL four weeks apart.

Note: The study is presented by Ph.D. student Dr. Marc Shamier, Erasmus MC, Rotterdam, Netherlands, from a research team led by Dr. Rory de Vries. No industry conflicts of interest were disclosed.