The promising results for two competing Covid-19 vaccines are raising hopes, but experts warn that there are still unprecedented challenges ahead.

Last week, Pfizer and BioNTech announced that their vaccine is more than 90 percent effective at preventing Covid-19, which was followed on Monday by Moderna declaring that its vaccine is 94.5 percent effective at preventing symptomatic cases, and seems to reduce the severity of cases. Although experts heralded the promising results, they also cautioned that developing effective vaccines is just one part of the picture.

After these vaccines are ready for the public—which will take months—the next stage will be rolling them out and getting people to take it. It will be a massive undertaking to build up healthcare infrastructure alongside one of the largest-ever public information campaigns. Read more at The New Republic.