If there's a sunny side to the major avian flu outbreak that is squeezing the nation's egg supply, it's this: You'll still be able to get your flu vaccine this fall, if you want it.
Egg prices have soared in recent weeks as the outbreak, the worst in three decades, takes its toll on the chickens that lay those eggs.
That's raised the question of whether the companies that make vaccines for human flu will be able to meet demand for the coming flu season. Most of the more than 150 million doses of human flu vaccine produced annually are grown over the course of months in eggs.
U.S. officials and major vaccine manufacturers told CNBC that they don't expect any problems meeting demand, given special environmental protective measures in place for the chickens that produce the eggs used in vaccine production. Manufacturers have in recent weeks begun shipping vaccine doses, which were in production as far back as March.
Tom Skinner, spokesman for the federal Centers for Disease Control and Prevention, said the CDC is "not aware of avian flu outbreaks affecting vaccine production."
An AstraZeneca spokeswoman said, "Eggs used to manufacture FluMist/Fluenz are not affected by the egg shortage." She added that the eggs used to produce those vaccines come from "specific pathogen-free chickens which are housed in entirely separate sites and facilities from chickens used for the food supply," which are the ones that have been affected by the avian flu virus.
"SPF chickens are kept under specific, very tightly controlled conditions that use filtered-air positive pressure housing, critical biosecurity measures and the careful selection of layer flocks," the spokeswoman said.
CSL Behring's spokeswoman said: "The production of our influenza vaccine will not be affected by the current egg shortage, either this upcoming season or future ones. Our 2015-2016 vaccine has already been produced, and we have our own isolated egg production system, keeping us secure for the future."
A spokeswoman for Sanofi Pasteur said the avian flu outbreak likewise "has not impacted the supply of Fluzone vaccines," and noted that the first of what the company has said will be more than 65 million doses began being shipped in mid-July.
"We continue to maintain preventative measures for our egg supply," she said.
A GlaxoSmithKline spokeswoman said, "GSK is monitoring the current situation with avian flu in the North American poultry population and we are reinforcing our stringent biosafety standards with our supply farms." The drug giant makes flu vaccines in facilities in Canada and Germany, which both rely on egg sources that are separate from "general commercial egg and poultry farms," the spokeswoman said.
"There hasn't been a decrease in the overall quantity of eggs needed or expected for production," she said.
GSK also noted that it expects to ultimately ship between 32 million and 38 million vaccine doses to the U.S. market this season. Last season, the company said it shipped about 27 million doses.
This season's shipments will be quadrivalent vaccines, which target four strains of flu. That's twice the amount of quadrivalent doses that GSK shipped last season.
The reassurances by manufacturers come after a challenging 2014-15 flu season, in which many people, particularly the elderly, fell victim to the emergence of a H3N2 strain of influenza that was different than the strains targeted by the existing vaccine. The season saw the highest recorded rate of flu-associated hospitalizations for people age 65 and older.
Improving on last year's vaccine
The CDC on Thursday issued an updated flu vaccine advisory for the coming 2015-16 season, noting changes to the composition of so-called trivalent vaccines, which contain three different strains. The H3N2 strain that emerged last season as well as B/Phuket virus have been added to the vaccines.
The agency also said, "Routine annual influenza vaccination is recommended for all persons" age 6 months and older "who do not have contraindications."
"Optimally, vaccinations should occur before onset of influenza activity in the community," the CDC said in its advisory.
Seasonal flu activity can begin as early as October, and run through as late as February.
"We want all people to go out and get vaccinated, particularly people who are in the high-risk categories," said Skinner. Those categories include the elderly, young children and people with underlying health conditions such as heart disease and diabetes that make them particularly vulnerable to the effects of the flu.
"Vaccination is the single most important thing that people can do to protect themselves from the flu," he said.
Skinner also said, "We say it's OK to get vaccinated as soon as [vaccines] become available."
In addition to preparing for the routine, seasonal flu, health officials also continue to ready for the possibility and risk of a pandemic, when a nonhuman form of influenza, such as avian flu, is transmitted to humans and then spreads globally.
The U.S. Health and Human Services Department noted that since 2004 it has partnered with the egg industry "to establish a year-round, secure egg supply which is available if needed for pandemic vaccine manufacturing."
"Currently, nearly 900,000 eggs are available daily in this program," according to the office of the assistant secretary for preparedness and response at HHS. The office said there is a "robust physical and biosecurity program for all flocks and incubation facilities that supply embryonated eggs for pandemic production."
Egg-free vaccines
The reliance on eggs to produce vaccines is potentially problematic because of the risk of a pandemic, the possibility of a shortage of eggs and limitations on what types of vaccine viruses can be grown in eggs, the CDC has acknowledged.
In light of that, the federal government in 2009 provided $147 million in funding to Connecticut-based Protein Sciences Corp. to help it develop a vaccine that is produced with recombinant DNA technology instead of eggs.
"They really wanted to have a backup," Manon Cox, CEO of Protein Sciences, told CNBC.
The Food and Drug Administration approved the company's vaccine, known as Flublok, in 2013 for people age 18 and over. So far it is the only flu vaccine that does not rely on eggs to be made.
"It is the wave of the future," said Cox, who noted that other vaccines are based on a technology that is more than 70 years old.
In an unusual move in June, the FDA granted Flublok regulatory exclusivity, which means that no other similar flu vaccine can win product approval from the agency before January 2025.
Still, Flublok's market share is relatively tiny.
The company hopes to ship 1.2 million doses for this season starting next week, Cox said. That's less than 1 percent of the overall flu vaccine market in the U.S.
But Cox says the company hopes to increase sales by appealing to customers and health providers who would be attracted by the presence of more active ingredients in the vaccine, and the lack of ingredients such as egg protein, mercury or antibiotics.
"We sell it as the pure choice," she said.
Protein Sciences is also hoping that the results of a clinical trial it released in late June will make Flublok a more attractive option for health providers, Cox said. The study of about 9,000 people age 50 and older, showed that 31 percent more people were protected from the flu by quadrivalent Flublok than by a traditional egg-based quadrivalent vaccine.
(CORRECTION: This year, GlaxoSmithKline will ship between 32 million and 38 million doses of quadrivalent vaccine. An earlier story misstated the amount.)