Declines in hepatitis A seen after routine vaccination initiated

CHICAGO – While study is still ongoing, early data seem to indicate that a recommendation by the Advisory Committee on Immunization Practices (ACIP) may have impacted on nationwide hepatitis A rates, according to researchers speaking here at the 37th National Immunization Conference.

AnneMarie Wasley, ScD, of the CDC, said after the hepatitis A vaccine was licensed for use in children older than 2, the ACIP urged targeted vaccination for adults in high-risk groups like travelers, men who have sex with men and injecting drug users, and routine vaccination of children in communities with high rates of hepatitis A.

Wasley said this strategy had a clear impact on disease rates, particularly in certain groups, like American Indians.

In the early 1990s, rates of hepatitis A in American Indians were six to eight times higher than the national average. However, following widespread vaccination, an unprecedented drop in rates was documented.

“In 2001, for first time ever, the hepatitis A rate of American Indians is below that of the national average,” Wasley said.

Despite successes in reducing those rates, this strategy had little effect on overall nationwide rates, since the percentage occurring in Native Americans was still relatively small.

However, it appears the routine vaccination of children in states with consistently elevated rates of infection – that is, at least 20 cases per 100,000 – is having an impact.

Since the recommendations have been in place, health officials have been monitoring surveillance data, and in addition to noting cyclic variation in the disease, they have seen rates decline precipitously.

“In states where routine vaccination was recommended rates fell by 83% by 2001, 85% in 2002, and hepatitis A rates fell by 76% where it was suggested that hepatitis A vaccines be considered. In comparison, the decline was only 40% where there was no suggestion of routine immunization,” she said.

Nationwide, most new cases of hepatitis A are now seen in states where routine childhood vaccination was not specifically recommended, and disease rates are highest among adult males in high-risk groups.

A dramatic example of the decline was seen in data presented from the California Department of Health, which reported that from 1990 through 1994, the rate of hepatitis A was 18.6 per 100,000. The rate fell 75% after the vaccine was added to the California Childhood Immunization Schedule, to 5.2 cases per 100,000.

For Your Information:

• Wasley A, Woodfill C, Pulido M. Hepatitis A: national, state and local trends in disease rates. Abstracts 108, 109. Presented at the National Immunization Conference. March 17-20, 2003. Chicago.