HIV viremia is rare, but possible, following mpox vaccination, Italian study finds

While rare, viral blips and failures do occur after people living with HIV (PLWH) are vaccinated against mpox, according to a recently published study conducted in Italy. Close viral load monitoring can identify such cases and, if necessary, treat them appropriately.

About This Study

“Viral blips and virologic failures following mpox vaccination with MVA-BN among people with HIV“ was published online on Sept. 29, 2023, in AIDS. The lead author is Angelo Roberto Raccagni, M.D., of the Vita-Salute San Raffaele University in Milan, Italy.

Key Research Findings

The study investigated viral blips or failures among 187 PLWH who were virally suppressed at the time they were vaccinated against mpox with the modified vaccinia Ankara-Bavarian Nordic (Jynneos) vaccine. One hundred forty-seven participants received two doses and 40 participants received a single dose of the vaccine because they had already been vaccinated against smallpox.

All but one participant was male. Although all participants were technically virally suppressed prior to vaccination, 37% of participants had residual viremia at baseline, which was defined as a viral load above the level of detection but below 50 copies/mL.

Overall, there were six viral blips (single viral load ≥50 copies/mL) and three virologic failures (viral load ≥1,000 copies/mL or two consecutive blips); two of the failures occurred after the second vaccine dose, and the individual who had virologic failure after one dose reported low compliance to antiretroviral treatment (ART). Both participants with viral failure after the second dose had residual viremia between dose one and two of the mpox vaccine, despite high ART adherence. The ART regimen was changed after viral failure, and all viral blips resolved within one month of vaccination.

Seven of the nine participants with blips or failures (78% of that group) had residual viremia before getting vaccinated, compared to 35% of participants who remained suppressed throughout the study. Blips or failure were also more common in PLWH with lower CD4/CD8 ratios and a previous AIDS-related event than those without such factors.

Discussion Highlights and Implications for Practice

Study limitations reported included the lack of unvaccinated controls and unstructured sampling for three months after vaccination, which may have missed viral blips.

Study authors recommended close monitoring of viral load after mpox vaccination to identify and treat rare cases of ART failure appropriately. Administering the vaccine at the person’s place of HIV care would facilitate such monitoring. Study results should be validated in larger cohorts.

By Barbara Jungwirth