Efficacy of mRNA vaccines in people with HIV or solid transplant recipients

Simon Collins, HIV i-Base

The first randomised data comparing the Pfizer and Moderna COVID-19 vaccines in people with immunosuppression related to HIV or solid organ transplant (SOT) is published this month in CID.

This was an open-label non-inferiority study in 412 people (341 HIV+ and 71 SOT) in Swiss HIV Cohort Study and the Swiss Transplant Cohort Study, who were randomised to either nRMA vaccine.

Baseline characteristics overall had a median age of 53 years (IQR: 43 to 61), 75% were male and 9% had a previous SARS-CoV-2 infection.

In the HIV cohort, only 2% (7/352) had a CD4 count <200 cells/mm3 with >91% being >500 cells/mm3; and 5% (20/352) had detectable viral load (>200 copies/mL).

Out of the 78 organ transplant recipients (41 lung, 37 kidney), 80% (62/78) were on an intensive immunosuppressive therapy.

In the combined analysis, both vaccines overall generated similar efficacy results for the primary endpoint of having a positive antibody response eight weeks after the second dose, meeting criteria for non-inferiority [92% vs 94%, diff 2.2% (95% CI, –7.1 to +2.7%)].

However, although 100% of participants in the HIV cohort generated antibody responses only 60% of the SOT group (95% CI: 49 to 72%; 43/71) had titres above the cut-off of 0.8 units/mL. The paper also notes that a higher cut-off might be needed to be clinically relevant.

Efficacy among the SOT group fell even further to approximately 40% and 20% when using more stringent antibody tests.

The five cases of COVID-19 reported during the study were all before receiving the second vaccine dose, with no hospitalisations. However, 18 participants had at least one serious adverse event (not judged related to the vaccines) and two participants died.


This small study is important for not showing significant differences between the two mRNA vaccines. It is underpowered however for the interesting between- and within-group analyses, for example, at low vs high CD4 counts or by donated organ (lung vs kidney) etc.

As with many HIV studies, most participants were on effective ART with high CD4 counts and undetectable viral load. It is frustrating that more details on the others were not included (for example on the range of low CD4 and high viral load counts.


Speich B et al for the Swiss HIV Cohort Study and the Swiss Transplant Cohort Study. Antibody response in immunocompromised patients after the administration of SARS-CoV-2 vaccine BNT162b2 or mRNA-1273: A randomised controlled trial. Clinical Infectious Diseases, 2022;, ciac169. (2 March 2022).

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