Background and challenges to implementation:
School-based tobacco prevention is often costly and does not harness the broad usage of smartphones in adolescence.

Intervention or response:
We took advantage of the widespread availability of mobile phones and adolescents' interest in appearance to develop a free selfie photoaging app "Smokerface" which is promoted via a poster campaign in secondary schools. This study involving 10,000 students in 126 German secondary schools aims to evaluate its effectiveness regarding smoking prevalence and students' attitudes towards smoking at two years follow-up.

Results and lessons learnt:
After one year of follow-up, preliminary results show good adhesion of the schools to the posters (110 schools of 126 fully comply with the study protocol), only seven dropped out. This is the first national study to show that current e-cigarette and cigarette smoking prevalence in grades 6 and 7 of secondary schools are the same (4.7% use cigarettes and 4.6% use e-cigarettes).

Conclusions and key recommendations:
Our research has the potential to pave the way for a new form of low-cost and broadly available school-based tobacco prevention in the form of poster campaigns promoting a free app. Our baseline analysis shows good comparability between the groups at baseline after randomisation and provides new insights into the prevalence of smoking and the use of e-cigarettes among pupils in the 6th and 7th grades in Germany.