A third dose of Pfizer and BioNTech’s COVID-19 vaccine reverses waning efficacy, restoring protection against the disease to 96%.

That’s according to the two drugmakers, which disclosed what they say are the first efficacy results from a large, randomized controlled COVID-19 vaccine booster trial. Participants who received a booster at least six months after initial two-dose inoculation with the drug increased protection to the levels achieved after the second dose, Pfizer announced Thursday. Their outcomes were compared to those of study participants who did not receive a third shot.

The trial involved 10,000 participants aged 16 years and older, and took place when the highly contagious delta variant was the prevalent viral strain, the company added. The third dose met its marks for safety as well. 

“These important data add to the body of evidence suggesting that a booster dose of our vaccine can help protect a broad population of people from this virus and its variants,” said Ugur Sahin, M.D., CEO of BioNTech.

The news may bring some comfort to long-term care staff and residents who recently received a third dose of the vaccine. Federal agencies greenlit the drug for booster use in late September. It has been the only COVID-19 vaccine officially sanctioned as a booster since.

The Food and Drug Administration this week recommended that Moderna and Johnson & Johnson vaccines be used as boosters, and the Centers for Disease Control and Prevention is expected to weigh in shortly with guidance.

In related news:

CDC panel endorses Moderna, J&J COVID vaccine boosters, mix-and-match strategy  Independent advisers to the Centers for Disease Control and Prevention on Thursday unanimously recommended that booster doses of Moderna and Johnson & Johnson COVID-19 vaccines be offered to certain eligible Americans. The booster shot could be matched with the same drug used initially or be different from the original vaccine, the panel advised. If CDC Director Rochelle Walensky concurs, the agency’s guidance will align with that announced by the Food and Drug Administration on Wednesday.