High demand for GlaxoSmithKlein's new and more effective shingles vaccine has created a shipping backlog that may leave some pharmacies temporarily without the needed doses.

The company has implemented order limits for the Shingrix vaccine that is expected to continue throughout 2018, according to the U.S. Centers for Disease Control and Prevention.

Shingles gets its start in childhood chickenpox. The virus goes dormant in the nerve cells only to be reactivated years later. People who live to age 85 and had chickenpox as children have a 50-50 chance of developing the excruciating rash. It can also affect the eyes and result in a complication called postherpetic neuralgia, a debilitating nerve pain.

"We have significantly increased deliveries and accelerated shipments of doses of vaccines for this year, and Shingrix is expected to be available throughout 2018 and shipped on a regular basis," said Sean Clements, spokesperson for GSK. He said the company had seen "an unprecedented level of demand" from patients and health-care providers.

Shingrix, a potential $1 billion-a-year drug to prevent the shingles virus in adults 50 and older, was approved by the Food and Drug Administration in October 2017.

As of May, more than 1.5 million people in the United States had received the vaccine, Clements said.

A quick check of some pharmacies in the Philadelphia region found the vaccine was still available, but not at all locations.

"We ran out last week," said Dave Scala, a pharmacist at the CVS store at 6501 Harbison Ave. in the city's Mayfair neighborhood. The store saw a number of requests for the prescription in the last three months. It currently has the drug back-ordered, he said.

A quick check of the 10 CVS pharmacies closest to the Harbison Avenue store found that seven had the drug in stock, Scala said.

"Whether a store has it depends on demand," Scala said. They all received similar shipments, he said.

The Rite Aid at 510 E. Baltimore Pike in Media, Delaware County, was out of Shingrix, but eight other Rite Aids within a 10-mile radius still had at least a few doses available, a pharmacist said.

GSK has recommended that people who need the second of the two-dose series of the vaccine get priority. They would have a window of two to six months after their first shot to complete the series, Clements said.

The current supply of Shingrix is sufficient to support the vaccination of more patients during 2018 than were vaccinated against shingles during 2017, the CDC reported.

Shingrix is not the only shingles vaccine on the market.

The drug company Merck offers Zostavax, which has been on the market for years. But protection from the virus decreases from 68.7 percent effectiveness the first year to 4.2 percent in the eighth year after vaccination, according to a Kaiser Permanente study of adults 60 and older, so Shingrix is preferred by many.