When new coronavirus variants emerged in Brazil, South Africa, and the U.K., vaccine developers wasted little time constructing plans to battle back. Now, companies including Moderna (MRNA -3.58%), Pfizer (PFE -0.43%), Johnson and Johnson (JNJ 0.06%), and AstraZeneca (AZN 0.07%) are working on updated vaccines and specialized boosters.

While they're perfecting new shots, the coronavirus continues to spread, and while it does, the threat of even newer strains emerging remains. This leaves public health experts and the average individual alike wondering: What's each business' expected development timeline for these new protective measures?