A third COVID-19 vaccine has been approved for emergency use in the U.S. after the FDA approved it on Saturday, Feb. 27. It is authorized to be administered to individuals 18 and older.

The vaccine, developed by Johnson & Johnson, requires only one shot and it’s trial of 44,000 people across the globe found it to be 66.1% effective against moderate to serious cases of COVID-19 after four weeks. Of those administered a trial of the vaccine in the U.S., it proved 72% effective and 86% protection against serious forms of coronavirus.

Pfizer and Moderna’s two-shot vaccines proved 95% effective at combating the virus, but medical experts warn such comparisons with J&J’s are misleading due to the timeframe when the three vaccines were tested in clinical trials.

J&J’s was tested when more contagious variants were more prevalent and sprouting at a rapid pace. Specifically, during testing in South Africa, most of the cases after vaccination were found to come from newer variants of COVID-19.

Pfizer and Moderna’s two-shot vaccine, while 95% effective, were clinically tested when less variants were present. There is still research to be done on how they affect both.

The new, one-shot vaccine has a limited initial dose count to start — at 4 million — but J&J expects to get 20 million distributed by the end of March. 

It has also signed a contract with the U.S. to provide 100 million doses by the end of June and the U.S. government has said it is working to help the company ramp up production.

Beyond the importance of having more vaccines available for distribution, the one-shot administration of the J&J vaccine will make it more accessible for more communities across the country.

Right now, those getting Moderna or Pfizer’s vaccine must get a first shot and then wait up to two weeks before being administered a second one.

The new vaccine also does not need to be transported at freezing cold temperatures to still be effective. Pfizer’s needs to be kept between minus-112 and minus-76 degrees Fahrenheit, and Moderna’s at minus-13 to minus-5. J&J’s is still effective after shipping at between 36 to 45 degrees Fahrenheit.

An advisory committee to the CDC met Sunday, Feb. 28 and will meet again on Monday, March 1 to discuss how the new vaccine will be used. The hope is to get the vaccine rollout started this week.