The U.S. could run into a vaccine supply predicament if an influenza pandemic hits, since only one drugmaker has a U.S. facility with egg-based vaccine production capabilities. Further, the situation could be even more serious if the epidemic comes from an avian flu, which could infect the very same hens that supply the eggs used for vaccine development. 

The observations come courtesy of a new U.S. Government Accountability Office (GAO) report (PDF) examining the country’s avian flu efforts, compiled as requested by Congress.

About 90% to 95% of the current national stockpile of pandemic flu vaccines is produced with chicken eggs, the report says, based on the account of a Department of Health and Human Services official. Four companies contribute to the stockpile, but only one has an egg-based vaccine manufacturing facility in the country.

The report didn’t identify that lone company, but Sanofi Pasteur has a site in Pennsylvania and has previously entered into HHS contracts to ensure egg supply for vaccine production. The report did point out that there are poultry raised specifically for producing eggs to make human vaccines. A Sanofi spokesperson declined to confirm whether the French drug giant is the company mentioned in the report.

Having domestic vaccine supplies is particularly important because, once a worldwide influenza pandemic hits, vaccines may be tough to come by, according to the report. In that case, "the U.S. government may not be able to rely on foreign countries to allow exports of pandemic vaccine," the authors state.

Therefore, the U.S. government only has one "dependable manufacturer for producing egg-based vaccine for rapid pandemic mitigation," said the report.

HHS is well aware of that risk and has contracted with Sanofi to ensure a year-round supply of eggs. In October 2010, HHS awarded a $57 million federal contract to Sanofi, renewing an older 2004 contract. In September 2014, the agency handed out another $42 million for the cause.

However, there is a solution to this problem: changing to cell-based or recombinant technologies to produce vaccines.

In 2012, FDA approved then Novartis’ Flucelvax, the first U.S.-licensed seasonal flu vaccine manufactured using cell culture technology. CSL has since picked up Novartis' flu offerings.

Just a few weeks ago, by request of HHS, Protein Sciences embarked on the development of two H7N9 vaccine candidates using recombinant technology. The vaccine maker touted the fast production of its recombinant vaccine compared to traditional egg-based flu vaccines.

Elsewhere, three Centers for Innovation in Advanced Development and Manufacturing are seeking to provide "a significant domestic infrastructure" in the U.S. for protection against bioterrorism and pandemic influenza, and potentially to assist with the phase-out of egg-based vaccines. The three locations include one in Texas by the Texas A&M University System, one Emergent Biosolutions’ facility in Maryland, and one in North Carolina that Australia's CSL bought in 2015 from Novartis together with the latter’s flu vaccine business.

But according to HHS’s Office of the Assistant Secretary for Preparedness and Response, it is still unclear when the three centers would be fully operational to be able to manufacture the contracted quantity of pandemic influenza vaccine.

Outside of the pandemic requirements, CSL's Seqirus unit did start providing the cell-based Flucelvax Quadrivalent vaccine, which was approved by the FDA last May, from the North Carolina facility for the 2016-2017 flu season.