Pfizer Inc said on Thursday its vaccine for respiratory syncytial virus (RSV) was effective among older adults in a late-stage study and it plans to file for approval with the U.S. health regulator in the coming months.

There are no U.S. approved vaccines for RSV, a common virus that typically causes mild cold-like symptoms but can be fatal for young kids and older adults. RSV is estimated to cause about 14,000 annual deaths among older adults in the United States.

Pfizer's vaccine was 85.7% effective among participants with three or more symptoms, and 66.7% for two or more symptoms, according to an interim analysis carried out by an external data monitoring panel.

The vaccine, RSVpreF, was also found to be well-tolerated with no safety concerns in the study.

Pfizer's shot is designed to target two strains of the respiratory virus. The company has so far enrolled about 37,000 participants aged 60 and above in its late-stage global study of the vaccine.

Rival Moderna also began a late-stage study of its messenger RNA shot for RSV in February.

Pfizer said it also plans to prepare submissions for approval of the shot to other regulatory authorities in the coming months.