Cases of hepatitis A have dropped dramatically in Southern California and much of the West over the last few years, and experts credit the decrease in large part to the widespread vaccination of children against the most common liver disease.
Most of the drop has been among Latino children, who had a rate of hepatitis so high that a UCLA medical school study of the pre-vaccine years of the early 1990s called it an epidemic.
Unlike inoculations for polio, measles and diphtheria that children are required to get before they can enroll in school, taking the vaccine for the most prevalent type of hepatitis is voluntary in California. However, most pediatricians and clinics have included it in the battery of childhood immunizations since the U.S. government made it widely available in the last few years.
In Orange County, the number of hepatitis A cases among Latinos 18 and younger has dropped 91% from 2000 to 2002, from 107 to 10, statistics show. In Los Angeles County, cases among Latinos 14 and under have dropped from 368 in 1999 to 114 in 2001, a 69% decrease. Only 52 cases were reported in 2002, according to preliminary Los Angeles County data.
When all of the data for 2002 are in, state health officials say they expect that for the first time there will have been more cases of hepatitis A in adults than in children.
"This is a very graphic example of the public health impact, the incredible power that vaccinations can have," said Dr. Beth P. Bell, chief epidemiologist in the National Center for Infectious Disease viral hepatitis division.
Hepatitis A is transmitted through fecal and oral contact, and is usually spread when carriers don't wash their hands, through contaminated food or water, or through sexual contact. About 100 people die from the disease each year in the United States, and on rare occasions a patient needs a liver transplant. Symptoms are similar to the flu, and also include jaundice. In most cases, rest is the only cure, and doctors can do little other than order blood tests to measure the progress of the infection.
Most people recover within three months, and the disease confers lifetime immunity.
Hepatitis A is less virulent than hepatitis B or C, but much more common. Hepatitis B and C each kill about 4,000 people a year. Like the AIDS virus, hepatitis B and C are spread by an exchange of body fluids, through sexual contact or sharing of needles, and from mother to fetus.
The hepatitis B vaccine has been available for 20 years and is required of children entering school in California.
Last year, no cases of hepatitis B were reported among Californians younger than 16.
While not as severe as the other liver diseases, hepatitis A takes a toll. Adults miss an average of 27 days of work, according to the Centers for Disease Control and Prevention.
In 1989, the federal agency estimated that hepatitis A cost more than $200 million a year in lost productivity.
The vaccine was approved by the Food and Drug Administration in 1995 but was used mainly by U.S. travelers visiting regions where the disease was widespread, such as Asia and Latin America.
Four years later, the federal Advisory Committee on Immunization Practices recommended that children in 11 states, all in the West except Oklahoma and South Dakota, with high hepatitis A rates be vaccinated.
That recommendation allowed the U.S. government to provide the vaccine free to state and local agencies to immunize poor children. Private physicians followed suit. By targeting children, epidemiologists say they are reaching the largest group at risk for the disease. And when children are infected with hepatitis A, often they do not show symptoms.
"The idea is if you vaccinate children, not only do you prevent infections in children, but you prevent them in adults," Bell said.
Children can be vaccinated at age 2, with two shots given six months apart. Several states, including Oklahoma and Alaska, have made vaccinations mandatory.
Although it remains voluntary in California, many doctors include hepatitis A shots among the 20 or so vaccinations youngsters receive.
Kaiser-Permanente officials estimate that 80% of the 2- to 4-year olds who belong to its HMO have been vaccinated. In the last three months, Kaiser also raised the age of children it routinely vaccinates to 8.
At the Orange County Health Care Agency's 17th Street clinic in Santa Ana, children are offered the vaccine when they come in for required immunizations, which are free.
Freda Montes, 8, who recently moved from Mexico to Santa Ana, had come to the clinic with her mother, father and aunt for a tuberculosis test and a hepatitis B vaccine so she could enroll at Taft Elementary School. She closed her eyes and steadied herself for another jab in her left arm, Part 1 of the hepatitis A regimen.
"With our patients, when they come in, we don't discuss much whether it's a requirement," said Mary Wright, immunization project coordinator for the Health Care Agency.
Latino children traditionally have had the highest hepatitis A rates. A paper by the UCLA Center for the Study of Latino Health and Culture found that the average annual pre-vaccine rate for Latino children in Los Angeles, Orange, San Bernardino, Riverside and San Diego counties was nearly six times that of other groups.
Epidemiologists say Latinos are more likely to live in crowded conditions, which helps spread the disease. The disease also is more common in Mexico, so if a child or relative travels there, they have a greater chance of contracting the disease.
Since vaccinations became widely offered, the hepatitis A rate among Latinos has plummeted. In 1990, 47 per 100,000 Latinos 18 and under contracted hepatitis A. The rate is expected to drop to four for 2002, said Celia Woodfill of the state Department of Health Services.
Nationally, the incidence of hepatitis A had already been declining since the mid-1970s, probably as a result of improved sanitation. It has dropped even lower since the vaccine became widely used.
In Orange County, the number of cases fell from 267 in 1999 to an estimated 91 in 2002, a 66% decline. Statewide, total cases for the same period dropped from 3,439 to 1,441, a 58% decline.
According to the CDC, hepatitis A cases in the states where vaccinations were recommended dropped 83% when the average rate from 1987-1997 is compared with 2001. Elsewhere in the nation, the rate fell 39%.
Epidemiologists are cautious about attributing the massive drop to the vaccine.
Still, "it's a little bit difficult to see how you could explain this magnitude of decline without expecting vaccination was playing some sort of a role," Bell said.