{"id":45180,"date":"2023-04-06T07:30:53","date_gmt":"2023-04-06T07:30:53","guid":{"rendered":"https:\/\/i-base.info\/htb\/?p=45180"},"modified":"2023-11-02T17:51:16","modified_gmt":"2023-11-02T17:51:16","slug":"uk-data-on-mpox-vaccine-efficacy-in-unadjusted-analyses","status":"publish","type":"post","link":"https:\/\/i-base.info\/htb\/45180","title":{"rendered":"UK data on efficacy of mpox vaccine: caution needed in observational analyses\u00a0"},"content":{"rendered":"

Simon Collins, HIV i-Base<\/strong><\/p>\n

\"\"<\/a>New data from the UK on the efficacy of mpox MVA-BN vaccine have been published in Lancet Infectious Diseases, together with an editorial comment that highlights major limitations in this and similar studies. [1, 2]<\/strong><\/p>\n

Estimating efficacy of this vaccine is complicated by a lack of prospective data, that the decline in mpox cases predated widespread access to the vaccine, and the significant differences in mpox risk factors between vaccinated and unvaccinated groups.<\/p>\n

The new dataset is based on self-completed questionnaires from roughly one-third of the cases reported in the UK from July to October 2022.\u00a0Overall, only 508\/1545 people with confirmed cases returned the questionnaire and the final analysis only included 363\/508 cases in gay and bisexual men who provided the required information.<\/p>\n

Of these replies, 322\/363 (89%) were unvaccinated, 8\/363 (2.2%) occurred at least 14 days after vaccination and 32 (8.8%) occurred within 13 days after vaccination. However, by October 2023, actual vaccine coverage was only 47%, so this would have been significantly lower for much of the study period.<\/p>\n

Vaccine effectiveness using this case-coverage design was based on coverage at 50% of an estimated 89,000 gay and bisexual men at risk. This compared vaccine coverage among cases with coverage in the eligible population.\u00a0Rates were also calculated for higher and lower coverage.<\/p>\n

Based on these data, three key results were reported.<\/p>\n