Is a mild flu season lulling America into complacency toward deadlier strains of the disease? Authorities are warning against ‘pandemic fatigue.’

Every year between October and May, the United States suffers the equivalent of a catastrophic terrorist attack or natural disaster in a major city. Some 36,000 people are killed and over 200,000 are hospitalized and between 5 percent and 20 percent of the population is affected—and yet we take it in stride and often ignore it.

This annual event is the onset of influenza, the respiratory flu that comes with cold weather.

The full scope of this year’s flu won’t be known until it is over in May and all the statistics are collected by the Centers for Disease Control and Prevention (CDC) in Atlanta, Ga., which tracks the disease. However, for the first time, this flu season more than 103 million doses of vaccine were distributed by November, with an additional 35 million doses capable of being manufactured if needed. That would be a record 12 million more doses than were produced in the 2006-07 season.

The numbers are important—widespread inoculation for the seasonal flu may help build resistance to the dreaded avian flu strain H5N1, a strain that continues to present a danger despite the onset of a mindset some health authorities characterize as “pandemic fatigue.”

Inoculation and resistance

Doctors at the CDC expressed hope this year that the extra vaccine capacity would result in “a record number of people getting vaccinated.” According to the CDC, 75 percent of the population should be inoculated.

And yet, even the CDC acknowledges that this hope may be wishful thinking. Even only an estimated 38 percent of physicians bother to get vaccinated, the agency says.

The statistics are similar among older Americans. According to an American Association of Retired Persons (AARP) survey in early December, far too many older adults are risking their health and the health of those around them by avoiding an annual flu shot. The AARP study found about half of people 50 and older did not get a flu shot last year, although vaccination reduces the risk of hospitalization for cardiac disease and stroke for people aged 65 years and older, studies show. Thirty-eight percent of those who reported not getting a vaccination last year said they believe they do not need one. Many others said they are concerned about the side effects, and more than 20 percent believe they could get the flu from the vaccine and do not trust the safety of the vaccine or are concerned about possible side effects.

Both the CDC and AARP have gone to great lengths to assure Americans of the safety of flu shots and the desirability of getting them. Federal health authorities have been pushing for the inoculation of more and more people, hoping to attain a higher level of protection against a pandemic flu should it break out during flu season.

It’s the same principle that’s in play with seasonal flu vaccines. If someone catches a flu strain that the seasonal vaccine was not designed to defeat, the inoculation will still provide a modicum of protection and the severity of symptoms may last only a few days, rather than week, and the length of time a person is contagious is shortened.

“Antibodies made in response to vaccination with one strain of influenza viruses can provide protection against different, but related, strains,” according to the CDC website, http://www.cdc.gov/flu/.

Children are another at-risk group which may not be getting enough flu shots. The CDC said the results of a study of data from the 2006 National Immunization Survey (NIS) “underscore the need to continue to monitor influenza vaccination coverage among young children, develop systems to provide childhood influenza vaccination services more efficiently and increase awareness among health-care providers and caregivers about the effectiveness of influenza vaccination among young children.”

The American Academy of Pediatrics and the Trust for America’s Health, meanwhile, stressed that public health experts recommend annual flu vaccines for all children with high-risk conditions who are six months of age and older, and all healthy children six months to five years old.

“CDC, state and local health departments should encourage and support seasonal flu vaccination clinics in school settings to maximize flu vaccine coverage rates,” the groups said in a joint statement.

But if problems with mass vaccination of children in New Jersey are any indication, authorities have their work cut out for them. At press time, Garden State parents erroneously concerned about vaccine side effects and government intrusion were trying to block the state from becoming the first state in the union to require flu shots for preschoolers, who health authorities agree should be vaccinated.

If similar widespread opposition erupts during a pandemic, the consequences could be horrific. In the event of a pandemic, it will be vital for children to be vaccinated. Studies show children and teens between birth and 19 years of age account for nearly 46 percent of all H5N1 flu deaths in the world.

The reason is individuals with healthy immune systems ironically are more likely to succumb to H5N1 because, unlike seasonal flu viruses, H5N1 upsets the chemical messengers that regulate immune function in a healthy, vigorous immune system. These chemical messengers activate an inordinate number of immune cells—called a “cytokine storm”—which causes pervasive inflammation and eventual death if not promptly treated with antiviral drugs. And antivirals aren’t an absolute guarantee of survival, authorities point out.

According to a team led by Menno de Jong of the Oxford University Clinical Research Unit in Ho Chi Minh City, Vietnam, “The focus of clinical management should be on preventing this intense cytokine response by early diagnosis and effective antiviral treatment.”

How close to pandemic?

Current testing shows bird flu strains are undergoing rapid and troubling mutations that are pushing the viruses closer to being able to be passed between humans. There have been at least two cases in which families transmitted H5N1 between them, experts believe.

Statistically, human-to-human transmission in these instances did take place, said Dr. Ira Longini Jr. of the Seattle, Wash.-based Fred Hutchinson Cancer Research Center.

“The world really may have dodged a bullet … and the next time we might not be so lucky,” Longini said, referring to a study of which he was senior author, published in the September issue of the CDC’s journal, Emerging Infectious Diseases (http://www.cdc. gov/eid/content/13/9/ 1348.htm).

Longini and others believe the study indicates a global pandemic was narrowly averted either because of quick action by health authorities or, more disturbingly, statistical good luck. Either way, scientists say the statistically relevant data confirm their private fears that some strains of H5N1 have been able to mutate into human transmissible form.