A third of vapers used high-strength nicotine in January this year compared to just 3.8 per cent on average between July 2016 and June 2021 with the biggest rise among 18-to-24-year-olds.A third of vapers used high-strength nicotine in January this year compared to just 3.8 per cent on average between July 2016 and June 2021 with the biggest rise among 18-to-24-year-olds.Read MoreHealth News | Mail Online