PHILADELPHIA (CBS) — The Food and Drug Administration said Wednesday that Johnson & Johnson’s COVID-19 vaccine provides strong protection against severe cases of the coronavirus. It could be available next week, if it gets emergency use approval.

The White House says it’s ready to go and that 3 to 4 million doses of the Johnson & Johnson vaccine will be released next week if it’s cleared by the FDA.

Experts say it will eventually help improve supplies and should make finding a vaccine a little easier.

Johnson & Johnson’s single-shot vaccine is injecting new hope in the fight against COVID-19.

The FDA says it’s met the requirements for emergency use authorization.

“There’s no question this vaccine is going to be a game changer,” said Dr. Mathai Mammen, global head of pharmaceutical research and development for Johnson & Johnson.

Johnson & Johnson says its vaccine is 66% effective in preventing moderate and severe COVID cases, and it’s 85% effective against the most severe symptoms.

“I think it’s great anytime we can add another vaccine to our tool kit here,” said Dr. John Wherry, director of Penn’s Institute for Immunology. “It’s really good news.”

Wherry says the Johnson & Johnson vaccine has two important advantages — it’s a single dose and can be stored in a regular refrigerator.

The vaccines from Pfizer and Moderna require two shots and freezers, but their efficacy rate of 95% is higher than Johnson & Johnson.

“I think it’s a small concern,” Wherry said when asked if it’s a concern that this vaccine is less effective than the other two. “All of these vaccines are really, really good at preventing the most severe complications of COVID-19 and that’s what we need to worry about.”

Wherry says Johnson & Johnson uses the standard vaccine formula, unlike Pfizer and Moderna that are made using the newer RNA technology.

He says availability should be the primary concern.

“We don’t have the luxury of having choices at this point,” Wherry said.

Johnson & Johnson says 20 million doses will be ready by the end of March, and that will be increased to 100 million in June.

The FDA found no serious safety problems with the Johnson & Johnson vaccine, but it can cause mild side effects like pain in the arm, headache and fatigue, similar to other vaccines.

The FDA could authorize the Johnson & Johnson vaccine as early as Saturday, depending on a vote by its advisory panel on Friday.

Stephanie Stahl