Single-blinded 1:1:1 block randomized controlled trial (with varying block sizes of 3-6), stratified by sex. A total of 60 participants will be recruited and randomly assigned with 20 in each treatment arm. Separated by three months, the participants will receive two doses of one of the following three treatments:
1. MMR vaccine (M-M-R VaxPro)
2. BCG vaccine (Danish strain 1331)
3. Saline (placebo)
