Immunizations (vaccines) expose the immune system to a potential future threat in order to “train” it to respond strongly later on. By training the immune system and exposing it to small amounts or inactivated versions of common illnesses, we may be able to avoid getting certain conditions entirely or experience a much milder version of the illness if we do get exposed.
How do vaccines work?
When a person receives a vaccine, their body mounts an immune response and starts creating proteins or immune cells designed to target whatever illness the vaccine is training the body to fight. Later on, if a person comes in contact with that same illness in the real world, their body will be already prepared to combat the infection before the individual gets very sick.1
Since vaccines require an active, healthy immune system to train, individuals with a weakened immune system (such as individuals with HIV) may not have as strong of a response to vaccines or may have an adverse reaction to certain vaccines if their immune system is too weak. Most individuals living with HIV, including both adults and children, can receive the routine vaccinations that the general population do unless they have a very low CD4 count or another barrier to vaccination.
Vaccines as part of HIV care
Getting vaccinated is important in HIV care. With a weakened immune system, illnesses that the general population can adequately fight, like the flu or pneumonia, may become life-threatening. Preventing these illnesses from happening to an HIV-positive individual in the first place (through vaccination) can greatly impact their overall health.1,2
What vaccines are not recommended?
Vaccines come in several forms and may be injected via a shot under the skin or into a muscle, given by mouth, or sprayed into the nose. Different vaccines have different methods of administration and have different timelines for when they should be given. Some vaccines are inactivated versions of the illness they’re designed to protect against. There is not much risk in getting these for a person living with HIV. The main concerns with an inactivated vaccine are injection site infections or a weakened response to the vaccine due to a weakened immune system.1,2
Other vaccines are live, attenuated vaccines. These vaccines may not be recommended for an individual living with HIV if their CD4 count is too low. Live, attenuated vaccines contain weakened forms of the illnesses they’re designed to protect against. In an individual with a healthy immune system, these weakened illnesses may have no impact at all on the person receiving them. In some cases, they may cause a mild form of the illness that is much less severe than if the person was to get the illness on their own in the community.1
For most, this is not a problem. However, if an individual with a weakened immune system was to get this weakened but live form of the illness, such as an HIV-positive person with a low CD4 count, they could get very sick. This is why some live vaccines, such as measles, mumps, rubella (MMR) vaccine, the varicella (chickenpox) vaccine, and the zoster (shingles) vaccine may not be recommended for individuals with a CD4 count less than 200 cells/microliter. If you are unsure whether or not you should receive a particular vaccine, ask your doctor or healthcare provider.1-4
What vaccines should an HIV-positive individual get?
As mentioned, as long as an HIV-positive individual has a relatively high CD4 count and/or is taking ART (antiretroviral therapy, medications used to treat HIV) to keep counts high, they should not have a problem getting the vaccines recommended to the general public. Many of these include:
- Influenza (flu)
- TdaP (tetanus, diphtheria, and pertussis)
- HPV (human papillomavirus—before age 26)
- HBV (hepatitis B)
- Measles, mumps, rubella (MMR—if CD4 count is greater than 200)
- Varicella (chickenpox—if CD4 count is greater than 200)1-4
Other vaccines may be recommended in specific situations, or if an individual may be exposed to a less common illness. Several of these include the hepatitis A vaccine or the Haemophilus influenzae b vaccine.3,4
When to get vaccinated
The best time to give an HIV-positive individual a vaccine is when their immune system is relatively strong. This occurs when their CD4 counts are high, or when they are regularly taking, and responding to, ART. However, it may be beneficial to give some vaccines regardless of CD4 count, such as the yearly flu vaccine, in an attempt to protect an individual as much as possible.
If a vaccine is given during a time when the immune system is weaker, and the body’s response to the vaccine was not that strong (meaning the person giving the vaccine may not have achieved full immunity) the vaccine may need to be repeated at a later time when the immune system is better prepared.1,2
Is there a vaccine for HIV?
At this time, there isn’t a vaccine that prevents HIV; however, scientists are currently investigating ways to develop one. Vaccines that help the immune system make more HIV-fighting proteins are currently being researched. In addition, vaccines that help strengthen the human immune system response to HIV are also being studied. These vaccines may help our bodies better fight off HIV, but further research is needed.5