Monkeypox MVA-BN® Vaccine Elicits Durable Immunity for 2 Years With Single Dose

Receipt of a single dose of the modified vaccinia ankara-Bavarian Nordic (MVA-BN^®) monkeypox vaccine was found to be associated with durable memory immune responses for up to 2 years. Increased concentrations of neutralizing antibodies also were observed following receipt of a booster dose. These study results were presented at IDWeek 2022, held from October 19 to 23, in Washington, DC.

The response to the monkeypox virus outbreak should optimally trigger broad rollout of monkeypox vaccines for populations at increased risk for infection.

The MVA-BN vaccine, developed by Bavarian Nordic, was evaluated in a clinical trial. Researchers randomly assigned vaccinia-naive participants to receive either 1 dose of the MVA-BN vaccine (n=181) or 2 doses in a 4-week interval (n=183). Participants (n=200) who were previously vaccinated against smallpox were also included in the analysis and received an MVA-BN boost dose. Subsets of vaccinia-naive participants who received 1 or 2 MVA-BN vaccine doses received a booster dose 2 years after initial vaccination. The primary outcomes were nAb responses at 2 years, and safety and efficacy of the 2-year booster dose.

Geometric mean titers (GMTs) of nAbs were 5.1 and 4.8 at week 2 among participants in the 1- and 2-dose groups, increasing to 7.2 and 7.5 at week 4, respectively. Among participants who received 2 vaccine doses, nAb GMTs peaked at 45.6 by week 6 and subsequently stabilized by week 8 at 34.0.

At 2 years, nAb GMTs were similar to baseline among participants in both the 1- and 2-dose groups.

Following receipt of a booster dose at 2 years, nAb GMTs peaked 2 weeks later at 80.7 and 125.3 among participants in the 1- and 2-dose groups, respectively. Post-booster nAb GMTs remained increased when assessed at 6 months among participants in both the 1-dose (25.6) and 2-dose (49.3) groups.

The most common adverse event following MVA-BN booster receipt at 2 years was erythema at the injection site (82.2%).

“These anamnestic responses support the presence of durable immunological memory in both groups,” the researchers noted. The responses following receipt of an MVA-BN booster dose “indicate that the approved 4-week interval of the two-dose regimen could optionally be extended up to at least 2 years,” the researchers concluded.

Disclosure: Multiple authors declared affiliations with industry. Please see the original reference for a full list of disclosures.