PfSPZ Vaccine, composed of radiation-attenuated, aseptic, purified, 
cryopreserved Plasmodium falciparum sporozoites, is administered by direct 
venous inoculation (DVI) for maximal efficacy against malaria. A critical issue 
for advancing vaccines that are administered intravenously is the ability to 
efficiently administer them across multiple age groups. As part of a pediatric 
safety, immunogenicity, and efficacy trial in western Kenya, we evaluated the 
feasibility and tolerability of DVI, including ease of venous access, injection 
time, and crying during the procedure across age groups. Part 1 was an age 
de-escalation, dose escalation trial in children aged 13 months-5 years and 
infants aged 5-12 months; part 2 was a vaccine efficacy trial including only 
infants, using the most skilled injectors from part 1. Injectors could use a 
vein viewer, if needed. A total of 1222 injections (target 0.5 mL) were 
initiated by DVI in 511 participants (36 were 5-9-year-olds, 65 were 
13-59-month-olds, and 410 infants). The complete volume was injected in 
1185/1222 (97.0%) vaccinations, 1083/1185 (91.4%) achieved with the first DVI. 
474/511 (92.8%) participants received only complete injections, 27/511 (5.3%) 
received at least one partial injection (<0.5 mL), and in 10/511 (2.0%) venous 
access was not obtained. The rate of complete injections by single DVI for 
infants improved from 77.1% in part 1 to 92.8% in part 2. No crying occurred in 
51/59 (86.4%) vaccinations in 5-9-year-olds, 25/86 (29.1%) vaccinations in 
13-59-month-olds and 172/1067 (16.1%) vaccinations in infants. Mean 
administration time ranged from 2.6 to 4.6 minutes and was longer for younger 
age groups. These data show that vaccination by DVI was feasible and well 
tolerated in infants and children in this rural hospital in western Kenya, when 
performed by skilled injectors. We also report that shipping and storage in 
liquid nitrogen vapor phase was simple and efficient. (Clinicaltrials.gov 
NCT02687373).