The aim of the study is to test a series of developed effective interventions targeting Danes going on vacation to sunny destinations to decrease sunburn by increasing use of shade, hats, protective clothing, and sunscreen to prevent skin cancer in the Danish population. It has been estimated that up to 90 % of all skin cancers could be avoided by behavioral changes. One of the main sources of UVR exposure in the Danish population is vacations to destinations with high UV index (UVI).

The aim of the study is to test a series of developed effective interventions targeting Danes going on vacation to sunny destinations to decrease sunburn by increasing use of shade, hats, protective clothing, and sunscreen to prevent skin cancer in the Danish population. To achieve the aim of this study we will conduct a randomized controlled trial with four arms during May-Dec 2018. Participants will be Danish adults traveling on vacation in 2018 for a period of 1-3 weeks, recruited from the civil registration system. After enrollment and pretesting, participants will be randomly assigned to one of four experimental conditions. Three experimental groups will receive innovative intervention strategies for promoting sun protection practices during vacation - Protection Routine (1), Protection Routine (2) or both Protection Routine (1+2). The fourth experimental condition will be a minimal treatment control group. The primary outcomes of the trial will be a reduction in frequency of sunburn by adherence to the current sun protection advice from the Danish Cancer Society, i.e., use of shade, hats, protective clothing, and sunscreen as secondary outcomes. We hypothesize that the following two interventions will be able to reduce significantly the UVR exposure and risk of sunburns in Danes going on vacation to destinations with high UVI.

The participants of the study are recruited from the Danish civil registration based system. The study population will represent all groups of the Danish population. Eligibility criteria for the project are persons living in Denmark going on vacation in May-December 2018 and having a smartphone compatible with either apple iOS (version 7.0 or newer) or Google Android (version 4.0 or newer). The period May to December is chosen as it includes all types of vacationers. The summer vacation constitutes the majority of the sunny vacations of the Danes. The period includes both the summer, where Danes typically travel to the Mediterranean area and the winter period where travel patterns change a bit to more exotic areas like Thailand, Egypt and the Canarias Islands. Exclusion criteria are persons younger than 18 years of age.

Sun protective behavior, exposure to UVR and sunburn will be evaluated by use of a questionnaire validated by personal electronic UV-measurements. This newly developed survey tool has made it possible in this project to evaluate the skin cancer interventions, without tracking of development of skin cancer which can take several years to develop after excessive UVR exposure. The short time period from intervention to evaluation minimizes recall bias.

The primary success criteria of the effectiveness of the interventions is a 10 % decrease in sunburn fraction in the intervention groups as compared to the control group in the post-intervention measurement, as shown possible in the pilot study.

Furthermore, we aim to reach completion and response rates of 90 % of the total sample

Secondary success criteria are increased awareness on the risk of skin cancer, increased use of protection (shade, clothes, hat and sunscreen) and decreased outdoor exposure when the UVI is highest between 12 and 3 pm. For all secondary success criteria, we aim for an improvement of 10 % between interventions and control group.

Inclusion Criteria:

• Travel for a vacation to a location with higher UVI than Denmark in the trial period (May-December 2018)
• Access to a smartphone compatible with either iOS (version 7 or newer) or Google Android ( version 4.0 or newer)

Exclusion Criteria:

• Physically or mentally uncapable to complete the planned intervention routines