Effectiveness of COVID-19 vaccines in people living with HIV in British Columbia: a test negative design


BACKGROUND: The efficacy of COVID-19 vaccines against severe disease, hospitalizations, and deaths were rapidly established in drug approval trials. Less is known, however, about their effectiveness among immunocompromised individuals such as people living with HIV (PLWH). We therefore sought to estimate the effectiveness of Pfizer-BioNTech (BNT162b2), Moderna (mRNA-1273) and AstraZeneca (ChAdOx1) vaccines in a population-based cohort against laboratory confirmed SARS-CoV-2 infections and hospitalizations among PLWH.
METHODS: We used the British Columbia (BC) COVID-19 Cohort (BCC19C), which integrates data on SARS-CoV-2 tests, COVID-19 cases, hospitalizations, and immunization with provincial health administrative data. PLWH status was assessed using an adapted version of a previously validated case-finding algorithm. All PLWH who were living in BC, '¥19 years old, and tested for SARS-CoV-2 between December 15, 2020 (when vaccines became available in BC), and November 21, 2021 (time before Omicron variant), were eligible.
Vaccine effectiveness (VE) was estimated by the test-negative design using multivariable logistic regression to compare the odds of vaccination between test-positive 'cases' and test-negative 'controls', adjusting for age, sex, area-level income, health authority, number of COVID-19 tests 3 months prior to study period, Elixhauser comorbidity index, and bi-weekly testing periods. We used the formula (1-AOR) x100% to compute VE.
RESULTS: There were 9,116 PLWH in the dataset, 2,657 (29.1%) of whom tested for SARS-CoV-2 during the study period and were considered eligible. Of the eligible PLWH, 357 (13.4%) tested positive (cases), while 2300 (86.6%) tested negative (controls); 68 (19.0%) of test positive cases and 254 (11.0%) of test negative controls were unvaccinated. Adjusted VE against SARS-CoV-2 symptomatic infection was 78.7% (95% CI = 63.6, 87.5) '¥ seven days after two vaccine doses. VE was preserved until the period four to six months following receipt of two vaccine doses after which slight waning was observed (VE = 66.4% (95% CI = 21.6, 85.6). Adjusted VE against hospitalizations was 88.4% (95% CI= 19.9, 98.3) '¥ seven days after two vaccine doses.
CONCLUSIONS: Findings suggest that receipt of two COVID-19 vaccines doses is effective against SARS-CoV-2 infections. Future efforts will focus on the impact of variants of concern on VE and comparing VE estimates with a matched HIV-negative cohort.

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