A healthcare worker conducts a PCR Covid-19 test at the Lancet laboratory in Johannesburg on November 30, 2021.

Rich countries can't say they weren't warned.

For almost as long as Covid-19 has been around, scientists, academics and campaigners have called on wealthy nations to share vaccines around the world — not only to protect people in those countries, but also to reduce the risk of new mutant variants emerging that could evade vaccines for everyone.