A recent study has analyzed adverse events following the Modified Vaccinia Ankara-Bavarian Nordic (MVA-BN) vaccination for mpox. The study was published in the Journal of American Medical Association (JAMA) and assessed adverse events following MVA-BN vaccination using data from AusVaxSafety, Australia’s vaccine safety surveillance system.
The researchers observed that local adverse events were the most common after intradermal MVA-BN vaccination. A 0.1 ml intradermal dose was recommended for pre-exposure prophylaxis due to the shortage of MVA-BN vaccines in the recent mpox outbreak in Australia, whereas a 0.5 ml subcutaneous dose was recommended for post-exposure prophylaxis in a two-dose regimen four weeks apart.
Participants received a survey link seven days after vaccination to complete a questionnaire on adverse events. Responses were considered for analysis if completed within seven days. The proportion of participants who reported adverse events, missing daily activities or medical review (visiting a clinician/emergency department or seeking medical advice) post-vaccination was evaluated. Of over 21,000 vaccinated subjects, there were 13,306 respondents, with a median age of 41.
Most respondents were males (97%), and MVA-BN was subcutaneously administered in 5,643 participants and intradermally in 7,663 subjects. The rate of adverse events was the highest after the first dose administered intradermally at 53% and the lowest after the second subcutaneous dose at 31%. The common adverse events with subcutaneous vaccination were local pain, redness, and swelling, while local redness, itching, and swelling were commonly reported after intradermal administration.
The rate of systemic adverse events was not different by vaccination route and was the highest after the first dose. Local adverse reactions were the highest after the first dose regardless of the route of administration but were overall the highest following intradermal vaccination. Cardiorespiratory adverse events were rare. Individuals with atopic dermatitis reported the highest rate of adverse events. Adverse event rates were similar between immunodeficient individuals and those without chronic conditions.
Only a small proportion of respondents reported missing activities due to adverse events post-vaccination. The rate of seeking medical review was low overall. The researchers observed that absolute event rates were much lower than previously reported. The percentage of people missing everyday activities or seeking medical review was low, indicating that the vaccine was well-tolerated.
In conclusion, the researchers observed that local adverse events were the most common after intradermal MVA-BN vaccination. The vaccine was well-tolerated, and the adverse event rates were much lower than previously reported. The study highlights the importance of vaccine safety surveillance systems like AusVaxSafety in evaluating adverse events following vaccination. These systems can help monitor the safety of vaccines and enable a rapid response to any adverse events.
