Now more than ever, some argue, there is a need for widespread vaccination against hepatitis A.
Since 1999, the Centers for Disease Control and Prevention and the American Academy of Pediatrics have recommended childhood vaccination in 11 Western states where incidence rates are twice the national average. But much of the responsibility for enforcing immunization falls on parents and schools, and vaccination recommendations can often go unheeded.
Some experts also say that focusing efforts in only a small number of states may leave millions of people vulnerable to the threat of contaminated produce shipped from regions where hepatitis A is endemic. Contaminated green onions from Mexico set off an outbreak in western Pennsylvania that killed 3 people and sickened over 600 others in late October. Smaller outbreaks in Georgia, North Carolina and Tennessee were also traced to Mexican scallions.
"The evidence shows that trying to focus on high-risk people has been only marginally successful over the years," said Dr. Michael Osterholm, a University of Minnesota epidemiologist. "Produce is emerging as an important cause of food-borne disease, and we have only a limited ability to affect conditions in those countries where it's coming from."
In October, as health officials scrambled to screen thousands of people for hepatitis A after the Pennsylvania outbreak, a group of doctors at the Children's Hospital of Pittsburgh released a study outlining the need to vaccinate all children over 2 years old.
In 1997, the last year for which figures are available, hepatitis A cost the United States about $489 million in work loss, lost productivity and medical costs, according to the study. Vaccinating children nationwide, according to the study in The Pediatric Infectious Disease Journal, would not only be cost-effective but would also prevent about 75,000 cases of the disease.
Vaccinating every child "would prevent twice as many cases than just vaccinating children in the 11 states with the highest rates," said Dr. David P. Greenberg, a vaccine expert at the children's hospital and a study author. "Years from now, if most adults and children are immunized, then an outbreak like the one in Pennsylvania could be avoided."
Hepatitis A is spread by fecal matter from infected people. Children, who often show few signs of the disease, tend to infect adults, who can suffer more severe symptoms. Adults who contract the disease in childhood are immune for life, providing protection in countries where hepatitis is widespread. But in the United States, where it is not as common, the disease can cause devastation because an outbreak can begin with a single infected person.
Dr. Paul Offit, a former member of the C.D.C. advisory committee that recommended the vaccine in 11 states, said the agency had gradually moved toward universal vaccination against hepatitis A in the last few years. Some school districts require students to receive the shots, but that varies by state.
Holding the agency back, he said, is uncertainty over the benefits of the vaccine compared with expenses. "It's a financial decision," said Dr. Offit, chief of infectious diseases at the Children's Hospital of Philadelphia. "The answer to the question of whether the vaccine is of benefit is yes, it only has benefits. But the government often bases a decision like this on whether it is cost effective."
Still, even if a nationwide plan were put into effect, says Dr. Dean Cliver, a professor of food safety at the University of California at Davis, its progress would be stifled by fears about vaccine safety. "People in this country are phobic about immunization," he said. "We really are losing ground on childhood vaccinations, mainly because of some bad misinformation."