A return to normalcy could bring a pre-pandemic crisis — youth vaping — back to a boiling point, experts fear, even as conflicting studies paint different pictures of how coronavirus affected everyday usage during lockdowns, particularly among teens.

Data from the United States Centers for Disease Control and Prevention released last December that e-cigarette use among American youths was down 25 percent during state-imposed shutdowns has been presented in public-health circles as a tiny silver lining to come out of a pandemic that ranks in the top 10 among human history’s worst plagues.