25 May 2021 

Encouraging results from the Pfizer-BioNTech COVID-19 vaccine in HIV-positive people

  • Studies of HIV-positive people who have received COVID-19 vaccines are scarce
  • Israeli scientists have studied 143 HIV-positive people who received the Pfizer-BioNTech vaccine
  • High levels of antibodies against SARS-CoV-2 were produced after the second vaccination

Although several large pivotal clinical trials of first-generation COVID-19 vaccines have been completed, detailed reports of the effectiveness of the vaccines in key populations, including HIV-positive people, have not been released by the manufacturers. To make up for this oversight, observational studies are being conducted.

Researchers in Israel have reported results in 143 HIV-positive people who received both doses of the Pfizer-BioNTech COVID-19 vaccine. The researchers reported that two doses of the vaccine were able to trigger the production of antibodies that can attack SARS-CoV-2, the virus that causes COVID-19. Side effects were generally mild and HIV viral load increased very modestly in 2% of participants.

Study details

Researchers at the Sheba Medical Center in Tel-Hashomer, Tel Aviv, provide care and treatment for many HIV-positive people in Israel. Once the Pfizer-BioNTech vaccine became available in that country, researchers offered it to HIV-positive adults who already had scheduled appointments for routine care at the clinic. A total of 143 HIV-positive people agreed to be vaccinated.

The average profile of participants upon entering the study was as follows:

  • age – 50 years (33% of participants were 55 and older)
  • 92% men, 8% women
  • major ethno-racial groups – 95% white, 4% African
  • body mass index – 25
  • CD4+ cell count – 700 cells/mm3
  • all participants were taking HIV treatment and 95% of them had an undetectable viral load (less than 40 copies/mL)
  • 14% of participants had other health conditions, such as high blood pressure, cancer, co-infection with hepatitis C virus, chronic kidney disease, obesity and stroke

For purposes of comparison, researchers assessed blood samples from nearly 400 healthy HIV-negative healthcare staff.

None of the participants had been infected with SARS-CoV-2 in the past.

The Pfizer-BioNTech vaccine is given in two separate injections, usually several weeks apart.


Fourteen days after the first vaccination, the following proportions of people developed antibodies against SARS-CoV-2:

  • HIV-positive people – 51%
  • HIV-negative people – 59%

In general, antibody levels were lower in HIV-positive people compared to HIV-negative people after the first dose of the vaccine. The researchers only assessed antibody levels shortly after each vaccination. It is possible that with longer time periods between the first and second vaccination, higher levels of antibodies may have been created.

Eighteen to 26 days after the second dose of the vaccine, the following proportions of people developed antibodies that attacked SARS-CoV-2:

  • HIV-positive people – 98%
  • HIV-negative people – 99%

Furthermore, antibody levels in the blood samples from both groups of participants were, on average, about five times greater after the second inoculation than after the first shot.

Focus on HIV

Researchers further analyzed the antibodies that were produced after the second vaccination and found that all but four HIV-positive people had antibodies that attacked SARS-CoV-2. Below is a brief description of the four people in whom such antibodies were not detected after the second dose of the Pfizer-BioNTech vaccine:

  • a 66-year-old man with a kidney transplant who was receiving three drugs to suppress his immune system so that it would not attack the transplanted organ
  • a 58-year-old man who was on dialysis
  • a 72-year-old man with coronary artery disease
  • a 64-year-old woman with arthritis who was taking the drug colchicine and who, according to the researchers, “developed severe COVID-19 four weeks after the second dose of the vaccine”

Low cell counts and antibodies

The number of people with relatively low CD4+ cell counts prior to vaccination was as follows:

  • less than 350 cells/mm3 – 12 people
  • less than 200 cells/mm3 – 3 people

According to the researchers, all of these people were able to produce high levels of antibodies that attacked SARS-CoV-2 after their second vaccination.


A common local side effect reported among HIV-positive people was pain at the injection site. However, this was generally mild and resolved in a day.

Fatigue and headache were common side effects after the first dose of the vaccine. After the second dose, fatigue and fever were common side effects. In most cases the fever was mild.

Three people developed tingling in nerves in the following parts of their bodies:

  • face – 1 person
  • vaccinated arm – 1 person
  • both arms – 1 person

This side effect resolved within 48 hours.

Doctors detected an increase in liver enzyme levels in the blood samples of two people, however, this resolved within a few days.

HIV-related measurements

CD4+ cell count

The average CD4+ count fell modestly from 700 cells/mm3 before vaccination to 634 cells/mm3 after vaccination. However, this was not associated with any overall decline in health. There was no significant change in the ratio of CD4 to CD8 cells, so the overall health of the immune system did not change. Altogether, this finding of a decreased CD4+ cell count should not be surprising. In a study of more than 40,000 HIV-negative people who received the Pfizer-BioNTech vaccine, a temporary decrease in lymphocytes was noted after vaccination, as reported here: The Pfizer-BioNTech vaccine.

Viral load

In three people who previously had undetectable viral loads, viral loads rose to 47, 52 and 92 copies/mL after their second vaccination. These changes were very modest.

In these three people, their CD4+ counts in the past (prior to their initiation of ART) had fallen below the 200-cell mark. This previous low level of CD4+ cells may indicate persistent immunological defects. However, evidence for such defects was not presented by the researchers.

Note that participants were only monitored for a few weeks after the second vaccination.

Bear in mind

Although the present study included only 143 HIV-positive people, its findings are very promising. The same team of Israeli scientists has begun a larger study with at least 500 HIV-positive people (Itsik Levy, MD, Sheba Medical Center, personal communication) and plans to monitor them for at least two years. Similar studies are needed with HIV-positive people who have received the Pfizer-BioNTech and other COVID-19 vaccines in different parts of the world.

Like many researchers studying the immune response to COVID-19 vaccines, the researchers in Israel focused on antibodies that can attack SARS-CoV-2. However, there is another immune response that may also be important to monitor—cellular immunity. For this type of immunity, cells of the immune system that can fight viruses—such as T-cells and natural killer cells—need to be studied. These cells can produce antiviral substances when attacking viruses or virus-infected cells. Assessing cellular immunity can provide additional information about how vaccines can confer protection against COVID-19. However, assessments of cellular immunity are more cumbersome and not all research labs do them.

The Israeli study has not yet been peer-reviewed. Its findings should therefore be treated as preliminary but very promising.

—Sean R. Hosein


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The Pfizer-BioNTech vaccineTreatmentUpdate 239

HIV and COVID-19TreatmentUpdate 238

Frequently asked questions about vaccines for the prevention of COVID-19 – CATIE

COVID-19 Vaccines – National Advisory Committee on Immunizations


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