Scarcity and a lack of outreach has left millions of immunocompromised Americans without access to the treatment.

The 27-nation bloc is battling with manufacturers over its spot in the priority list for receiving COVID vaccines.

With shortfalls in vaccine supplies, countries across the world are concerned about getting their fair share of doses.

The COVID-19 vaccine is being produced so quickly due to a combination of factors involving the research community, government, industry and the public.