Distance runner Bernard Lagat (USA), 400m runner Kevin Borlee (BEL), pole vaulter Katerina Stefanidi (GRE) and middle distance runner Aisha Praught-Leer (JAM) were also elected, and attended their first Athletes' Commission meeting in Monaco today.
They joined six serving members with two years left on their terms - Inaki Gomez (CAN), Kim Collins (SKN), Adam Kszczot (POL), Thomas Rohler (GER), Ivana Spanovic (SRB) and Benita Willis (AUS).
Six further members were recently appointed to the Commission by the Council - Majd Eddin Ghazal (SYR), Olga Rypakova (KAZ), Akani Simbine (RSA), Su Bingtian (CHN), Milcah Chemos Cheywa (KEN) and Marie-Josee Ta Lou (CIV).
The Council is able to appoint up to six extra members to ensure that there is sufficient diversity within the athlete group to represent all disciplines and areas of the world.
The importance of athletes to decision-making within World Athletics was recognised and enshrined in legislation as part of the governance and integrity reforms approved in December 2016.
Under the 2019 Constitution, the Chairperson and one other member of the Athletes' Commission - one male and one female - become full voting members of the IAAF Council.
World Athletics president Sebastian Coe welcomed Lavillenie and Adams to the 26-member Council, saying he expected they would make a substantial contribution to the sport's decision-making body.
"Since my own competition days, I have been a strong advocate for athletes having a voice within sport," Coe said. "We want our athletes to be leaders and to contribute their opinions on the issues and challenges we face in steering a global sport with 214 member countries in a rapidly changing world. That will only make athletics stronger and more relevant to coming generations."