What does it mean when someone has developed no antibodies to the hepatitis B vaccine in spite of having the three recommended doses of the vaccine? Recent immune tests done on my five-year-old grandson showed no antibodies, and the attending physician wrote "no protection."

J.

No vaccine is 100 percent effective in preventing disease. In some vaccines, such as that for hepatitis B, most of the vaccine failures (the people who develop hepatitis B despite vaccination) are in people who never responded to the shots in the first place. In other vaccines, such as chickenpox and influenza, it is possible to respond well to the shot, yet still develop infection if exposed.

In the case of the hepatitis B vaccine, one can measure antibodies (proteins the body produces to prevent and fight infection) after the shots are given and determine whether the person has responded. Over 95 percent of healthy people will develop these protective antibodies and become essentially immune to infection. People who have immune-suppressing illnesses and those on hemodialysis for chronic kidney failure are less likely to respond to the vaccine.

The hepatitis B vaccine is given in three doses over several months. Experts do not recommend that the average person be tested for immunity after receiving the standard vaccine. However, testing is recommended for health-care workers, patients with chronic kidney failure and others at risk of repeated exposure to the hepatitis B virus. In people who are tested after vaccination and found not to have sufficient antibody, repeated vaccinations can sometimes produce immunity. One to three additional doses of vaccine can induce immunity in up to 50 percent of these people.

Most seemingly healthy people who do not initially respond to the vaccine do not have an underlying immune-suppressing illness. In other words, in most patients who have an underlying illness that prevents the vaccine from working, the illness is obvious. In the healthy nonresponders, a harmless genetic defect is often responsible for their lack of response to the vaccine. This defect does not predispose the person to any other problems. There is really no need to evaluate people for this abnormality, either, as there is no harm to the patient except lack of response to the vaccine.

Another cause of lack of response could be technical errors in the administration of the vaccine. The vaccine should not be administered in the buttocks because the effectiveness rate may be lower.

What you should do is the following: Ask your grandson's physician if there are any signs of immune deficiency in the boy. (I often order routine blood counts as a screening test for obvious immune deficiency, recognizing that the chance of finding something is low. It is not recommended to perform advanced immunity testing in all vaccine nonresponders, because the yield would be very, very low.) Then, I would ask the physician to consider a repeat vaccination to try to increase the chance of your grandson becoming immune to this infection. If that does not work, there is not much else you can do for now. There are several new vaccines being tested that may offer a better chance of response in your grandson, but it will probably be several years before they are available.