Some farms that feed cows in yards already use food additives that help reduce methane production in a cow’s stomach, but they have downsides, such as variable efficacy and the need to be constantly supplied, which is difficult if the animals are free to roam.

A vaccine could be an alternative, and the Pirbright Institute in the UK, a virology lab focusing on livestock, is leading a three-year study to develop one. “The appeal of a vaccine as part of the solution is that it’s a very well adopted, common practice, with infrastructure able to do this already, and people know about the benefits of vaccination for animal health generally,” says John Hammond, director of research at The Pirbright Institute.