(Bloomberg) -- Pfizer Inc. will run out of several doses of penicillin, which treats syphilis, strep throat, and other infections, later this year as shortages ripple across the US’s antibiotic supply.

The company anticipates running out of the children’s dose of the syphilis drug Bicillin L-A by the end of June, according to a Pfizer letter posted Tuesday on the Food and Drug Administration’s website. The company says it’s prioritizing production of larger doses of Bicillin L-A, which is recommended for pregnant people with syphilis because it is the only drug that can pass through the placenta and also treat the fetus.

A different Pfizer penicillin, Bicillin C-R that treats other bacterial infections but not syphilis, is expected to run out in the third quarter, which ends Sept. 30. Pfizer’s penicillin has been in shortage since April.

“The supply interruption is the result of a complex combination of factors including significant increases in demand, due to an increase in syphilis infection rates as well as competitive shortages,” Pfizer said in the letter, which is dated June 12.

Basic antibiotics have been in short supply in the US since October, when rising rates of respiratory infections led to increased demand for amoxicillin, the most popular antibiotic. Shortages of the children’s form of this drug led to more need for antibiotics like penicillin, which treats similar infections.

Drug shortages are at a five-year high, according to the University of Utah’s drug information service, which tracks shortages. Congressional committees and a White House task force are working on addressing this problem, which has plagued the industry for over a decade.

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