Healthy 18 to 55-year-olds are being invited to take part in a human challenge study in London that will see them infected with the H3N2 flu strain, which is currently the most common in the UK.Healthy 18 to 55-year-olds are being invited to take part in a human challenge study in London that will see them infected with the H3N2 flu strain, which is currently the most common in the UK.Read MoreHealth News | Mail Online