An early, severe flu season and higher-than-anticipated demand have resulted in some shortages of vaccine, setting off a last-minute scramble in the Washington area and nationwide, according to health officials, doctors and retailers.

Manufacturers have already shipped more than 128 million doses of flu vaccine, nearly 95 percent of the 135 million doses made for this season, federal officials said. Sanofi Pasteur, the largest flu vaccine provider in the United States, said Thursday that it had sold out of four of its six vaccine versions. It made more than 60 million doses for this season, slightly fewer than last year.

Now, in response to “unanticipated late-season demand,” Sanofi said it will make available a limited supply of additional vaccine originally intended for shipment outside the country. Those orders would start shipping in late January, spokesman Michael Szumera said.

Another supplier, Med­Immune, has sold all 12 million doses that it planned to distribute but has more than 620,000 extra doses, a spokeswoman said.

Manufacturers are not able to make any more vaccine for this season — the process is too long and complicated, and they are already preparing for next year. “You have to have the right kind of egg from the right kind of chicken, then grow the virus and purify it,” said Carolyn Bridges, associate director for adult immunization at the immunization services division of the Centers for Disease Control and Prevention.

This flu season is having its earliest start in nearly a decade.

In a frantic search for vaccine, many consumers in the D.C. region Thursday swapped tips, scoured Web sites and badgered pharmacists and doctors. A pediatric practice in North Bethesda directed patients to Shady Grove Adventist Hospital in Rockville and an urgent-care facility in Bethesda.

Public health officials urged residents to use ­flushot.
, an online flu vaccine locater, to find a provider.

Vaccine hunters

Among the vaccine hunters was Emily Dillon, 22, a resident of Northwest Washington who works for a nonprofit organization downtown and has been trying to get a flu shot since Sunday.

First she tried two CVS stores, one in Bethesda and one in Rockville, but they had no vaccine. Then her mother started looking on her behalf and found out the Safeway in Columbia Heights was receiving a shipment Thursday. But the store wasn’t taking appointments, Dillon said, and she wasn’t able to go after work.

“I have yet to get one,” she said. “But I’m going to keep plugging away.”

Some, like Dillon, were enlisting family members and friends in the vaccine quest because of long telephone wait times and inaccurate information posted in stores and online. Others were finding it hard to get work done because so many people are out sick.

Even though this season’s vaccine is well-matched to the predominant strain of virus circulating, at least 29 states were experiencing high levels of influenza-like illness as of Dec. 29, according to the latest data compiled by the CDC. Officials in Boston declared a public health emergency. Eighteen Massachusetts residents have died of flu-related complications this season, a state official said, and some hospitals in the state are changing their visiting policies to limit potential exposure to flu-causing viruses.

Virginia and Maryland are both reporting unusually high and widespread levels of flu-related illness. As of Thursday, hospitals in the District had reported 310 confirmed cases to the D.C. Health Department, more than triple the number of flu cases reported for the entire season last year.

In the past, vaccine shortages cropped up because of problems with production or with the vaccine itself. But there were no such problems this season, officials said.

“What we do see is more demand than was anticipated” based on orders for vaccine that were placed in spring 2012, said Bridges, of the CDC.

In the Washington area, several CVS and Giant stores say they are running out of vaccine and scrambling to restock. A CVS spokesman said high demand caused by the early influenza outbreak has left some locations with “intermittent, temporary shortages of flu vaccine.” The company has more vaccine in stock, however, and anticipates providing more than 3 million shots this season, he said.

A spokesman for Giant said the grocery chain has “adequate inventory” in its Baltimore distribution facility. Store pharmacies could be experiencing shortages for a day or two while awaiting deliveries.

In Montgomery County, all five hospital emergency rooms reached capacity at one point Monday evening — in part because of the number of patients complaining of flulike illnesses. As a result, some ambulances may not have been able to take patients to the nearest hospital during the crush, officials said.

In early December, the CDC said it was noticing an uptick in flu activity about a month before authorities typically see it. The primary strain this season is H3N2, an influenza A virus that has been associated with more severe flu seasons.

Crowded emergency rooms

The CDC, which tracks pediatric deaths from the flu, said 18 children died nationwide between Sept. 30 and Dec. 29. In Pennsylvania, a total of 22 people have died from the flu, the Allentown Morning Call reported. Emergency rooms have gotten increasingly jammed, the newspaper said, prompting a local hospital to set up a tentlike mobile emergency room outside its main facility to handle flu patients.

The flu season runs from late September through late May, and influenza typically peaks in January, February or later.

“While it’s not too late to get vaccinated, it is late as far as our vaccination season goes, and people may have to look around to find vaccine,” said Thomas Skinner, a CDC spokesman. About 112 million Americans had been vaccinated by the end of November, the CDC said. Vaccinations are recommended for everyone 6 months or older.

Flu vaccines are designed to protect against three influenza viruses that experts predict will be the most common during the upcoming season. The three viruses that commonly circulate among people today are influenza B, influenza A (H1N1) and influenza A (H3N2). Each year, one flu virus of each kind is used to produce seasonal influenza vaccine.

The maker of Tamiflu is also reporting shortages of its liquid formulation, which is used mainly to treat symptoms in children. Roche Holding AG said it informed wholesalers and distributors in recent weeks that they would face temporary delays in shipments, Reuters reported. Pharmacists can create a substitute by dissolving Tamiflu capsules into a sweet liquid.

The Food and Drug Administration on Dec. 21 expanded the approved use of Tamiflu to treat children as young as 2 weeks old who have shown symptoms of the flu. The drug was previously approved to treat adults and children at least 1 year old. The dose for children younger than 1 must be based on their exact weight.

Flu is extremely unpredictable. Last winter’s flu season, for example, began late and was unusually mild. It set a record for the lowest and shortest peak of influenza-like illness.

The last time a regular flu season started this early was the winter of 2003-04, which proved to be one of the deadliest seasons in the past 35 years, with more than 48,000 fatalities. The dominant type of flu then was the same one seen this year.

But experts said there is a critical difference: In 2003-04, the vaccine was poorly matched to the predominant flu strain. Also, health officials said more vaccine was available this year, and vaccination rates have risen for the general public and for key groups such as children, pregnant women and health-care workers.

Flu symptoms can include fever, cough, runny nose, head and body aches, and fatigue. Some people also suffer vomiting and diarrhea, and some develop pneumonia or other severe complications.

A novel strain of H1N1 influenza caused an unusual wave of cases in spring 2009 and again in the early fall, eventually causing a worldwide epidemic. Called “swine flu” by the media, it was the product of a reshuffling of genes from pig, bird and human flu viruses. The combination was sufficiently different that a new vaccine had to be made specifically to protect against it. That so-called pandemic H1N1 strain has been part of the flu vaccine for the past three years.

Debbi Wilgoren and David Brown contributed to this report.