Hamaluba M
Sang S
Orindi B
Njau I
Karanja H
Kamau N
Gitonga JN
Mugo D
Wright D
Nyagwange J
Kutima B
Omuoyo D
Mwatasa M
Ngetsa C
Agoti C
Cheruiyot S
Nyaguara A
Munene M
Mturi N
Oloo E
Ochola-Oyier L
Mumba N
Mauncho C
Namayi R
Davies A
Tsofa B
Nduati EW
Aliyan N
Kasera K
Etyang A
Boyd A
Hill A
Gilbert S
Douglas A
Pollard A
Bejon P
Lambe T
Warimwe G
COVVaccine Trial Group
Wellcome Open Res. 2023;8182
BACKGROUND: There are limited data on the immunogenicity of coronavirus disease 2019 (COVID-19) vaccines in African populations. Here we report the immunogenicity and safety of the ChAdOx1 nCoV-19 (AZD1222) vaccine from a phase 1/2 single-blind, randomised, controlled trial among adults in Kenya conducted as part of the early studies assessing vaccine performance in different geographical settings to inform Emergency Use Authorisation. METHODS: We recruited and randomly assigned (1:1) 400 healthy adults aged >/=18 years in Kenya to receive ChAdOx1 nCoV-19 or control rabies vaccine, each as a two-dose schedule with a 3-month interval. The co-primary outcomes were safety, and immunogenicity assessed using total IgG enzyme-linked immunosorbent assay (ELISA) against SARS-CoV-2 spike protein 28 days after the second vaccination. RESULTS: Between 28 (th) October 2020 and 19 (th) August 2021, 400 participants were enrolled and assigned to receive ChAdOx1 nCoV-19 (n=200) or rabies vaccine (n=200). Local and systemic adverse events were self-limiting and mild or moderate in nature. Three serious adverse events were reported but these were deemed unrelated to vaccination. The geometric mean anti-spike IgG titres 28 days after second dose vaccination were higher in the ChAdOx1 group (2773 ELISA units [EU], 95% CI 2447, 3142) than in the rabies vaccine group (61 EU, 95% CI 45, 81) and persisted over the 12 months follow-up. We did not identify any symptomatic infections or hospital admissions with respiratory illness and so vaccine efficacy against clinically apparent infection could not be measured. Vaccine efficacy against asymptomatic SARS-CoV-2 infection was 38.4% (95% CI -26.8%, 70.1%; p=0.188). CONCLUSIONS: The safety, immunogenicity and efficacy against asymptomatic infection of ChAdOx1 nCoV-19 among Kenyan adults was similar to that observed elsewhere in the world, but efficacy against symptomatic infection or severe disease could not be measured in this cohort. PAN-AFRICAN CLINICAL TRIALS REGISTRATION: PACTR202005681895696 (11/05/2020).
