Q and A


Do HIV positive people need a third vaccine dose against COVID-19?

Hi, I have been seeing lots of news about a third dose. Do HIV positive people need a third vaccine dose?

My CD4 count is 430 and I have been undetectable on ART for about 20 years.


UPDATE 1 September 2021:

The UK government included HIV in the health conditions for a third dose. This will mainly be for people with a CD4 count below 200 cells/mm3, but your HIV doctor decides this. Please contact your HIV doctor if you have a low CD4 count or of conditions that mean two doses might not have been enough.

BHIVA statements on access to third doses. 


Thanks – there are lots of overlapping issue to your question.

The simple answer is that some HIV positive people would definitely benefit from a third vaccine dose. But definitely not everyone, at least not yet, and not based on available evidence.

Based on your CD4 count on ART, it is likely that you already have a strong response to the vaccine. There is no urgency for you to need a third dose, though we have little evidence to support this yet.

But if you were over 80 (maybe over 70 or 60) then your risk means a third dose might be important. Or if you have other health conditions, such as having had an organ transplant. Or if you are on cancer chemotherapy.

The third vaccine dose is a key topic right now and almost every day new papers are published.

Although these are more technical reports, the August issue of HTB has 5-6 articles and links about this.
HIV Treatment Bulletin (August 2021)

The small group of people with either no or very low responses after two shots can definitely benefit. There have been several studies that already showed this, including from France, Israel and the US. [1]

But there is no good data on HIV. We know that at high CD4 counts people seem to get similar immune responses to vaccines as HIV negative people. [2, 3]

We also know that immune responses are undetectable or much lower with very low CD4 counts. [4]

But not much to inform the majority of us whose CD4 counts are between 50 to 500. Or to say where the CD4 cut off is. If my CD4 count was less than 50 cells/mm3, I would act as if I had not had any vaccines. I don’t worry about my history of a CD4 count below 50 though, but we have no data on this yet.

Immune responses to the vaccines are definitely lower in people older than 80, where risks of COVID are highest. People older than 80 should get a third shot because cases have been reported of fully vaccinated people in this group who have still caught COVID-19 and died. [5]

As the risk of serious COVID-19 in HIV positive people happens at a lower age than similar HIV negative people, it is reasonable to think that the data in HIV negative people older than 80 might be similar to HIV positive people older than 70, or maybe lower still at 60. [6]

This is probably why the US CDC includes HIV positive people in the risk groups for getting a third vaccine. This is also likely in the UK. [7, 8]

Plus, the overlapping issue of lower immune responses from all vaccines against the Delta variant. Importantly though, the lower immune response is to symptomatic infection – preventing hospitalisation is still very high. [9]

As if this wasn’t already complex enough, there are also commercial interests.

So although Pfizer have got a lot of publicity about applying to the FDA for a third dose, this is based on very little data showing need. Firstly Pfizer disclosed this is a press interview, not a formal press release. Second, the limited data on waning antibody responses come from unpublished studies from the Israel vaccine programme, and then, two days ago, from their own phase 3 study. [10]

In the phase 3 study, efficacy drops from 96% to 84% for symptomatic infections but doesn’t report reduced efficacy against hospitalisation. This paper, not yet peer reviewed, says further follow-up to two years is needed before knowing whether a third booster dose is needed. [10]

Pfizer should submit safety data on the third dose for people who need this for people with significantly reduced immune systems. But this is very different to asking the FDA to change the label to routinely be a three-dose vaccine schedule.

This would generate huge profits for Pfizer and more seriously would destablise global access to vaccines when so many countries already have such terrible levels of access.

This answer was updated in September 2021 from an original question from July 2021.


  1. Third dose of mRNA vaccine improves antibody responses in kidney transplant recipients
  2. Antibody responses to Pfizer vaccine in HIV positive people with high CD4 counts
  3. Similar immune responses to the Oxford/AZ COVID vaccine reported In HIV positive and HIV negative participants
  4. Failure of mRNA vaccines to produce antibody responses in late diagnosed HIV with low CD4 count and high viral load
  5. Cases of COVID-19 reported including deaths in care home residents after full-course vaccination
  6. HIV is linked to higher mortality from COVID-19 compared to HIV negative: 60% of deaths were black ethnicity
  7. US CDC recommends third vaccine dose in some groups
  8. Plans for universal third vaccine dose for UK adults from September
  9. Efficacy of Oxford/AZ and Pfizer vaccines against Delta variant in the UK
  10. Pfizer plans for third dose: questions over population need?


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