ABSTRACT
Methane (CH 4 ) is well known as a component in the exhaled breath of humans. It has been assumed for a long time that formation of CH 4 in humans occurs exclusively by anaerobic microbial activity (methanogenesis) in the gastrointestinal tract. A fraction of the produced CH 4 is excreted via the lungs and can then be detected in the breath. However, recent studies challenge this view by showing that CH 4 might also be produced endogenously in cells by oxidative-reductive stress reactions. Thus, an increased and fluctuating level of breath CH 4 compared to the base level of an individual might also indicate enhanced oxidative stress levels. Thus, monitoring breath CH 4 levels might have great potential for ‘in vivo’ diagnostics. Generally, vaccines generate a strong immune response including the production of pro-inflammatory cytokines. To evaluate the effect from current vaccines against COVID-19 on breath CH 4 dynamics, breath CH 4 was monitored from 12 subjects prior and after the injection of several COVID-vaccines. Prior to COVID-19 vaccination the concentration of breath CH 4 was frequently measured by gas chromatograph flame ionization detection (GC-FID, with analytical precision better than 10 parts per billion, ppbv) to obtain the individual variation range of breath CH 4 for each subject. Following vaccination, CH 4 breath samples were collected at high frequency for a period of 14 days. All subjects monitored showed a strong response in breath CH 4 release within 1 to 72 hours after vaccination including shifts and high fluctuations with maximum peaks showing a factor of up to ±100 compared to base values. Thus, it is highly likely that the observed changes in breath CH 4 are coupled to immune responses following Covid-19 vaccination. These preliminary results strongly support the hypothesis that non-microbial methane liberation and utilisation in the human body might be also linked to cellular processes and stress responses independent of classical microbial methanogenesis. Thus, CH 4 might be used as a breath biomarker for specific immune responses and individual immune states.