Safety and immunogenicity of fractional COVID-19 vaccine doses in Nigerian adults: A randomized non-inferiority trial
Abstract
Abstract Fractional dosing of vaccines is a viable strategy to extend COVID-19 vaccine supplies in resource-constrained settings. We did a triple-blinded, multi-site, randomized non-inferiority trial in Nigeria (PACTR202206754734018). Adults 18–65 years received full, half, or quarter primary doses of ChAdOx1 or Ad26.COV2.S, or full vs half doses of BNT162b2. Primary study outcome was seroconversion defined as ≥ 2.5-fold rise in anti-Spike IgG geometric-mean fold rise (GMFR) at day 28. A total of 1894 participants were enrolled between June 21, 2022, and January 25, 2023. 320 participants in the fractional dose group and 220 in the standard dose group completed follow-up and were included in the analysis. Seropositivity at baseline was high, at 68% (365/539). Seroconversion was comparable between standard and fractional doses (p = 0.822). For ChAdOx1, 31% achieved seroconversion at standard dose (16/52), 28% at half-dose (15/53), and 34% in quarter-dose (18/53). For Ad26.COV2.S, the proportions were 27% (28/105), 32% (22/68), and 30% (21/71) respectively. For BNT162b2, the proportions were 43% (27/63) and 39% (29/75) for standard- and half-dose. Serum neutralization showed ≥ twofold response across dosing. There were no serious adverse events. Fractional vaccine doses generated non-inferior immune responses compared to standard doses in the context of previous COVID-19. Protocol Registration: The protocol was registered with the Pan African Clinical Trials Registry (PACTR) PACTR202206754734018.
Article Details
Authors (45)
Abideen Salako
Adesola Musa
Fehintola Ige
Adam Abdullahi
Ayorinde James
Sabdat Ekama
Oluwatosin Odubela
Ifeoma Idigbe
Olusola Ajibaye
Mazharul Altaf
Kazeem Adeneye
Folahanmi T. Akinsolu
Ifedola Olojo
Azuka Okwuraiwe
Henry Egharevba
Magaret Ekpenyong
Uchenna Elemuwa
Ifeoma Ezenyi
Fraden Bitrus
Olayemi Odubela
Abdulrasheed Oba
Ganiu Idris
Jimoh Yusuf
Ibukun Akande
Stephine Nwaiwu
Louisa Omale
Oluwatobiloba Oyewunmi
Adedoyin Agbabiaka
Olajumoke Eyinade
Joy Ogunwale
Abdullah Garba
Yahya Bello
Baba Musa
Ogochukwu Ezejiofor
Ben Ejiro
Bamidele Iwalokun
Leah Rosenzweig
Obi Adigwe
Christianah Adeyeye
Faisal Shuaib
Witold Wicek
Yohhei Hamada
Oliver Ezechi
Ravindra Gupta
Babatunde Salako