Chlamydia is the most common infectious agent that causes ophthalmia neonatorum in the United States, where 2%-40% of neonatal conjunctivitis cases are caused by Chlamydia

Reference: https://www.healthline.com/health/sexually-transmitted-diseases/chlamydia-vs-gonorrhea

Chlamydial ophthalmia (caused by Chlamydia trachomatis) is the most common bacterial cause; it accounts for up to 40% of conjunctivitis in neonates < 4 wk of age. The prevalence of maternal chlamydial infection ranges from 2 to 20%. Chlamydial ophthalmia usually occurs 5 to 14 days after birth. It may range from mild conjunctivitis with minimal mucopurulent discharge to severe eyelid edema with copious drainage and pseudomembrane formation. Follicles are not present in the conjunctiva, as they are in older children and adults. Gonococcal ophthalmia causes an acute purulent conjunctivitis that appears 2 to 5 days after birth or earlier with premature rupture of membranes. The neonate has severe eyelid edema followed by chemosis and a profuse purulent exudate that may be under pressure. If untreated, corneal ulcerations and blindness may occur. Although gonococcus is the second commonest organism responsible for ophthalmia neonatorum, it is the most virulent infectious agent for neonatal conjunctivitis.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4170304/