Study shows that most post-vaccination monkeypox infections occur within two weeks of receiving the first dose of MVA-BN

Study shows that most post-vaccination monkeypox infections occur within two weeks of receiving the first dose of MVA-BN

In a recent study published in JAMA Network Researchers described human monkeypox virus infection after vaccination with the modified Vaccinia Ankara-Bavarian Nordic (MVA-BN) vaccine.

Lernen: Infektion mit dem menschlichen Affenpockenvirus unmittelbar nach Erhalt des modifizierten Vaccinia-Ankara-Impfstoffs. Bildnachweis: PhotobyTawat/Shutterstock

background

MVA-BN is a live, non-replicating vaccine that protects adults from infection with smallpox and monkeypox. While immunogenicity studies indicate significant response rates following the two-dose series of MVA-BN vaccination, there is little evidence of efficacy in clinical use. As local health departments struggle to obtain MVA-BN, many have adopted a single-dose strategy to make the most of current supplies. Additional strategies for intradermal administration of lower volume doses have also been used.

About the study

The present study described monkeypox infections observed after a single dose of MVA-BN.

Howard Brown Health (HBH) began using real-time reverse transcriptase-polymerase chain reaction (RT-PCR) testing to identify monkeypox in May 2022. On June 28, 2022, HBH began distributing MVA-BN to qualified individuals. The study included people who tested positive for monkeypox between June 28, 2022 and September 9, 2022, at least one day after receiving the first dose of MVA-BN.

All cases of monkeypox-positive cases during the study period were retrieved from the electronic medical record (EMR). The EMR and a study of a statewide computerized database of vaccination records exchange were then used to determine the patient's vaccination status.

After vaccination, confirmed monkeypox cases were divided into four groups based on the number of days to positive results: one to seven days, eight to 14 days, 15 to 28 days and more than 28 days. The EMR was used to extract information on demographics, human immunodeficiency virus (HIV) status and virologic suppression, and use of HIV pre-exposure prophylaxis.

Results

During the trial period, 7,339 people at HBH received their first dose of MVA-BN, while 400 patients tested positive for monkeypox. Of the 90 people who tested positive for monkeypox at least one day after vaccination, 73.5% had a viral load of less than 200 copies/mL, 91% were cisgender, and 37.8% had HIV.

The team found that 37 cases occurred one to seven days after vaccination, while 32 cases were reported eight to 14 days after vaccination. This accounted for 77% of all cases diagnosed after vaccination. It took an average of 8.5 days from vaccination to infection. In addition, 36.2% of cases occurring 1 to 14 days after vaccination were HIV-positive individuals, 96% of whom were virologically suppressed. Pre-exposure prophylaxis was used by 54% of early revaccination cases without HIV infection.

Two cases of monkeypox occurred more than 14 days after the second MVA-BN dose and were included in the total of eight cases diagnosed 28 days after the first MVA-BN vaccination. All eight patients were cisgender men, 50% of whom had HIV and were virologically suppressed. Less than ten lesions were observed in all but one patient. Due to the severity of his anogenital symptoms, one patient received the antiviral drug tecovirimat.

Diploma

Overall, study results showed that most monkeypox-positive cases detected after MVA-BN vaccination occurred within two weeks of the first dose, before the vaccine was likely to be fully effective.

Reference:

• Hazra, A. et al. (2022) „Human Monkeypox Virus-Infektion in der unmittelbaren Zeit nach Erhalt des modifizierten Vaccinia Ankara-Impfstoffs“, JAMA. doi: 10.1001/jama.2022.18320. https://jamanetwork.com/journals/jama/fullarticle/2797135

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