Johnson & Johnson's Covid-19 vaccine Saturday. It is the first single dose Covid-19 vaccine available in the US, and is one that "checks nearly all the boxes."

With more than 28.5 million confirmed Covid-19 cases and over 511,000 reported deaths in the US since the start of the pandemic, and while the demand for vaccine still far exceeds supply, these vaccines can't come soon enough.

"A third safe and effective vaccine is very welcome news," Andy Slavitt, the White House's senior for Covid Response, tweeted on Friday.The vaccine, made by Janssen, J&J's vaccine arm, is safe and effective, and it's considered flexible. It's a single dose, and it doesn't require special storage.The vaccine is authorized for people ages 18 and older.

"We need a vaccine that can be quickly mass produced," Dr Greg Poland, head of the Mayo Clinic's Vaccine Research Group, said Friday. "We'd want to see a reasonable duration of efficacy and protection.They thought they were being vaccinated. It was a trial.
The vaccine was tested in more than 44,000 people in the US, South Africa and Latin America. Globally, it was 66.1% effective against moderate to severe/critical Covid-19 at least four weeks after vaccination, according to an FDA analysis. In the US, it is considered 72% effective, and offered 86% protection against severe forms of the disease.

"One dose will keep you out of the hospital, keep you out of the intensive care unit, and keep you out of the morgue," Dr Paul Offit, a vaccine adviser to the FDA, told CNN's Wolf Blitzer on Friday.

The vaccine comes with few side effects, most of which are mild, including pain at the injection site, headache, fatigue and muscle pain.