Vaccination in HIV

Things got off to an early start this morning at EACS, starting with 4 different ‘Meet the Expert’ sessions to chose from. I attended the session on vaccination in HIV.

This session provided a nice overview of recommended vaccinations and their rationale in HIV positive patients. This was a good reminder to me to ensure patients are appropriately vaccinated at baseline and to intermittently check antibody status where indicated. In a day and age where many patients seem to be commencing antiretroviral therapy so early in their care (and at increasingly higher CD4 counts), it is easy to forget that such individuals still carry an elevated risk of complications.

Four Cases

Four cases were used to demonstrate infections that were preventable through vaccination. The first case was about measles. The presenter highlighted the fact that in some European countries, up to 13% of patients with HIV have no detectable antibodies against measles (particularly in patients born after 1983).

Many patients are unsure of their vaccination history and it may therefore be important to check antibody status. Another important consideration relates to the measles vaccine being a live attenuated vaccine (along with Yellow fever and varicella). European guidelines recommend only using live attenuated vaccines in people well controlled on ART with CD4 counts >200 (14%), or off ARVs with higher CD4 counts (500, >20%).

The presenter suggested considering antibody titres where indicated. However, it is important to remember that antibody responses are used as a surrogate marker and may not reflect impaired cell-mediated immunity in HIV positive patients.

The second case was a reminder to ensure all patients with HIV have an annual influenza vaccine. They highlighted a study which showed no increase in immunogenicity through booster doses or increased antigen dose of influenza vaccine in HIV positive patients.

The second presenter discussed a case of a patient with pneumococcal pneumonia. Whilst the most vulnerable patients are those with low CD4 counts and those not on ART, strep pneumonia remains a problem even in the HAART era, with patients with HIV at greater risk of complications. I found this particularly interesting as I feel there is a lot of uncertainty around appropriate pneumococcal vaccine choice and timing in patients with HIV. 

In patients with HIV, conjugate vaccines (such as 13-PCV) have been shown to have greater immunogenicity (compared with polysaccharide vaccines such as 23-PPV) and it is for that reason they are recommended for initial vaccination where available in the EACS guidelines (and DHHS). EACS guidelines do not recommend booster doses at present. whereas the DHHS guidelines do. 23-PPV can be given 8 weeks after 13-PCV (or after CD4 increases over 200 on ART). In patients who has 23PPV initially, 13-PCV can be given after 1 year. The full DHHS guidelines can be found here: http://aidsinfo.nih.gov/guidelines

The final case discussed was around hepatitis B vaccination. Serological responses to standard dose vaccines are impaired in HIV-infected individuals (with lower response in low CD4 setting and off-ART). There are numerous schemes for non-responders which can be used - one study showed good response (86%) with re-vaccination with the standard schedule (especially if less than 3 months from the last dose of first schedule). Additionally, both double-dose schedules and intradermal vaccination showed improved response rates.

If you made it to the end of this blog, my take home points from this session were: 

• don’t assume prior vaccination (particularly with primary vaccines), take a full vaccine history and check titres where indicated
• use live attenuated vaccines with caution and as per guidelines
• conjugate vaccines appear to have higher immunogenicity and are therefore preferred (e.g. pneumococcal vaccine)
• double dose Hep B vaccinations in non-responders are easy to administer and show improved response rates