Update: As of this afternoon the Pokémon Pass app has been released in the US for download on iOS and Android devices. A trailer has also been released, which can be viewed below.
A brand new event has been announced for Pokémon: Let's Go, Pikachu! and Pokémon: Let's Go, Eevee! owners in the US. The event gives fans the chance to get their hands on a shiny Pikachu or shiny Eevee depending on which game you own. If you own Let's Go, Eevee! then you'll be given a shiny Pikachu and for Let's Go, Pikachu! you'll obtain a Eevee.
The event will begin on the 11th of May and run through a new app called Pokémon Pass. With the app downloaded you must then head to your nearest Target store where you can scan an exclusive QR code. This gives you a serial code that you can then enter into your game to redeem the special Pokémon.
The event ends on the 23rd of June, so plenty of time to get your hands on one of these shiny Pokémon. Pokémon Pass itself seems likely to stick around for future events. Also, it's worth noting that so far this event and Pokémon Pass have only been announced for the US. We'll bring more news as it comes!
(Image from @Tsukento on Twitter)