Vaccines for COVID-19: Pfizer, Moderna, and AstraZeneca Race to Finish Line .

Positive early results from Pfizer and Moderna’s mRNA vaccines brought global optimism, with both reporting protection rates above 94% in large phase III trials and no major safety concerns. These vaccines work by delivering mRNA encoding the SARS-CoV-2 spike protein, offering a fast, non-infectious platform but one that has never before reached widespread human use. While their point estimates far exceed WHO and FDA efficacy thresholds, key details—such as confidence intervals, durability of protection, and impact on asymptomatic infection—remain unknown. Logistical challenges also loom, particularly the ultra-cold storage required for Pfizer’s product. As these vaccines move toward authorization, ethical questions arise about how future trials can fairly compare new candidates to placebo when effective vaccines already exist, creating potential barriers to ongoing vaccine development.