Johnson & Johnson announced Friday that its single-shot coronavirus vaccine was 66% effective in protecting against moderate to severe COVID-19 disease in Phase 3 trials, which was comprised of nearly 44,000 participants across eight countries.

Between the lines: The vaccine was 72% effective in the U.S., but only 57% effective in South Africa, where a more contagious variant has been spreading. It prevented 85% of severe infections and 100% of hospitalizations and deaths, according to the company.

The big picture: The vaccine is not as effective as some of its two-dose competitors, but still provides strong protection against the most serious COVID-19 symptoms.

• J&J’s vaccine, which results in development of neutralizing antibodies, is long-lasting and doesn’t require freezing like Moderna and Pfizer-BioNTech’s shots, per Bloomberg. The vaccine can be stored at refrigerator temperatures for three months.
• The company said it will file for emergency use authorization from the FDA within a week. The U.S. has purchased 100 million vaccine doses from J&J.

What they're saying: "The J&J vaccine turns in a fantastic result. We now have 3 highly effective vaccines. This vaccine showed sustained (and increasing!) immune protection over time, perhaps from a robust early induction of memory immune cells (CD4 and CD8)," tweeted former FDA commissioner Scott Gottlieb.

• "This one shot vaccine was highly effective at preventing severe disease, even with new variants. The milieu of disease now is more complex; even in U.S. - trials done today are running into more mutated cases. Make no mistake: this is an important and wonderful development."