The New York Times reported that more than 58 million farmed birds in 47 states and birds in the wild have been affected, and it has spilled over into mammals, such as mink, foxes, raccoons and bears. Nine cases of avian flu have reportedly been diagnosed in humans in the last 15 months, but there is no sign that it is spreading person to person. If chickens are required to get vaccinated, they are likely to be banned for export.

Mass-vaccinating birds has the potential to reduce the severity of avian influenza but not halt transmission. Zoetis, the largest producer of medicine and vaccines for pets and livestock, is lobbying the Biden administration to adopt a a universal vaccine program for chickens. Zoetis split from parent company Pfizer in 2013. Zoetis' CEO, Kristin Peck, is a board member at BlackRock.

In 2005, World Health Organization warned that vaccinating chickens against the avian flu was actually contributing to the spread of the disease.

Nearly two decades later, a large spike in avian flu cases, the death of tens of millions of chickens and the steep increase in egg prices are among factors driving the Biden administration to consider mass vaccination of poultry, though no decision has been made and other ideas are circulating, too.