Newspapers and television news stations have been reporting for weeks about the shortage of influenza vaccines in the U.S.—and Americans’ sometimes frantic attempts to get a flu shot.

But just how big a deal is this national shortage?

According to Dr. Neil Fishman, an expert in infectious diseases at Penn, it’s a very big deal indeed.

And the worst part is, he says, it could have easily been avoided.

“This is a potential public health crisis,”says Fishman, director of the Department of Healthcare Epidemiology and Infection Control for University of Pennsylvania Health System. “The answer to the question of [how bad] hinges on what type of flu season we have.”

Fishman says the vaccine shortage—caused by the discovery that 48 million doses from British manufacturer Chiron Corp. were contaminated—has left America extremely vulnerable as the annual influenza season approaches. And about all the medical community can do, Fishman says, is wait, and hope it doesn’t take too heavy a toll.

Fishman says the still-young flu season of the Southern Hemisphere—sometimes used to predict the severity of the U.S. flu season— has been mild, giving hope to some health professionals that the same moderate conditions will take shape here. But Fishman says that recent reports warn of a new flu strain—potentially making the season worse—and trying to predict how hard hit we will be is a difficult task anyway.

“It has traditionally been very difficult to predict accurately,”he says.

Fishman says the U.S. government’s failure to invest in the public health structure has put the public at risk for no reason. Countries such as Canada, he says, have devised ways of ensuring citizens’ access to vaccines, so there’s no reason the U.S. can’t do the same.

Further, the inability to provide enough vaccines for a yearly, easily predictable occurrence such as the flu leaves him wondering whether the U.S. could handle a more unpredictable, more serious public health threat.

“We know that influenza occurs every year, once a year, and yet we’re not prepared for it,” he said. “This really raises significant questions in my mind as to how we could handle bioterrorism events. It also highlights the frailty of our vaccine supplies … [because] we as a nation have not invested in the public health structure.”

Regardless of the reason for the situation, Fishman says, the bottom line is that many U.S. citizens this year won’t get their flu shots, and they’ll have to do what they can to stave off the illness without it. Fishman suggests several “common sense” methods for doing just that—avoiding those who are sick, washing hands regularly and putting simple “good health habits” to use.

That means getting enough sleep, eating right and staying in shape. He also says people should avoid touching their eyes, nose or mouth.

And, should they get sick, he encourages them to stay at home, thereby preventing others from getting ill.

“A lot of these ideas are really simple and pretty common sense,” he said.

“But they can really help prevent the spread of germs.”