How Does a Vaccine Work?
When any infectious organism enters your body, the proteins of that organism stimulate the body to produce antibodies that fight off the organism. In addition, memory cells are also produced which remain in the host well after the organism has been eradicated from the body. It's these memory cells that recognize the organism the next time it enters the body and dispatches existing antibodies that prevent another infection.A vaccine fools the body into thinking it has been infected. The body believes infection has occurred and begins to produce antibodies and memory cells to fight the infection. In the case of hepatitis B vaccine, the body believes it has been infected with hepatitis B, so it produces antibodies to fight that infection. In the future, if an actual hepatitis B exposure does occur, the antibodies that have been produced as a result of the vaccine prevent hepatitis B infection.
When Vaccines Don't Work
In order for vaccines to be effective, they must trigger the body's immune response. In the case of a healthy, normal functioning immune system, this will occur most of the time. But in people who have weakened immune systems, such as people living with HIV, the immune response might not occur, therefore antibodies that protect the person from infection are not produced, leaving the person susceptible to infection. In the case of the hepatitis B virus, the vaccine might not trigger the immune response and therefore the person can still be infected with hepatitis B if exposed to the virus.Understanding the Immune Response
Double Dose Hepatitis Vaccine May Help
A few years ago, if there was no immune response to the hepatitis B vaccine, the person was just left susceptible to the hepatitis B virus. Now there is another option. Many studies have shown that giving a double dose of the hepatitis B vaccine series may elicit an immune response in people who don't respond to conventional hepatitis B vaccine dosing. The standard vaccine dose is a series of three 20 microgram (mcg) doses; one at month 0, then a second at 1 month, and the final dose at 6 months. About 90 percent of all people with normal immune systems will have a immune response to standard dosing. For those people not responding to the standard dose, a series of three 40mcg doses (again, at month 0, 1 month, and 6 months) can be given. There is data that shows that for some people living with HIV, these double doses can trigger the immune response necessary to protect them from hepatitis B in the future.What the Studies Show
- A study done at the University Medical School of Sao Paulo showed that double-dosing did trigger an immune response in a greater percentage of HIV infected people than did conventional dosing. However, the double dose made a difference in immune response primarily in people with CD4 counts above 350. Those with CD4 counts less than 350 did not show an appreciable difference between standard and double dosing. Interestingly, having a HIV viral load less than 10,000 also seemed to help the immune response when using the double dose.
- A study of people with weakened immune systems as a result of chronic liver disease saw a favorable response to hepatitis B double-dosing without any side effects or adverse reactions to the additional vaccine.
What is a CD4 Count and Why is it Important?
Ask Your Doctor About Double Dose Hepatitis B Vaccine
If you have had the hepatitis B vaccine series, ask your doctor if your body responded and if you are protected against the virus. The doctor can determine this by a simple blood test that looks for hepatitis B antibodies in your blood. If antibodies are present then you responded to the vaccine and you are protected. If your doctor finds out you have not responded, ask him or her about double dose hepatitis B vaccine. Depending on your CD4 count, it may be an option for you and an opportunity to get the protection you need.Sources
