Background: The popularity of the magnetic vaccine conspiracy theory, and others of a similar nature, creates challenges to the promotion of vaccines and the dissemination of accurate health information. Objective: Health conspiracy theories are gaining in popularity. The objective of the study was to evaluate the Twitter social media network related to the magnetic vaccination conspiracy theory and to apply social capital theory to analyse social structures. As a strategy for online public health surveillance, we employ social network analysis to identify the important opinion leaders sharing the conspiracy, the key websites, and the narratives. Methods: A total of 18,706 tweets were retrieved and analysed using social network analysis. Data were retrieved from June 01 to June 13 (2021) using the keyword 'vaccine magnetic'. Tweets were retrieved via a dedicated Twitter Application Programming Interface (API). More specifically, the Academic Track API was used, and the data were analysed using NodeXL Pro and Gephi. Results: There were a total of 22,762 connections between Twitter users within the dataset. The study found that the most influential user within the network consisted of a news account that was reporting on the conspiracy. There were also several other users that became influential such as an epidemiologist, a health economist, and a retired sports athlete who exerted their social capital within the network. Conclusions: Our study finds that influential users were effective broadcasters against the conspiracy, and their reach extended beyond their own network of Twitter followers. We emphasise the need for trust in contact with influential users concerning health information, particularly in the context of widespread social uncertainty resulting from the pandemic, when public sentiment on social media may be unpredictable. The study highlights the potential of influential users to disrupt information flows of conspiracy theories due to their unique social capital.