A possible alliance was first mooted in PRWeek last month, when Red Door owner Creston closed its US office (PRWeek, 22 February).
'The partnership builds on our international capabilities by giving us an experienced partner in the US,' said Red Door MD Catherine Warne.
Red Door has been expanding its international reach in healthcare comms with clients including Astellas, Boehringer Ingelheim and Bausch & Lomb.
Cooney/Waters Group, founded in 1992, provides PR and PA services to pharma and biotech companies globally. Each firm has a staff of around 50, specialising in healthcare PR and medical education and covering ethical and consumer health.
- Separately, healthcare comms agency Aurora has joined the network GlobalHealthPR as its UK partner.
Aurora MD Claire Eldridge said: 'Aurora delivers pan-European and global PR campaigns for clients. GlobalHealthPR provides us with greater market insights and will enable us to implement campaigns that are culturally relevant to the US, and major European, Latin American and Asian markets.'