• Vaccine Name: PfSPZ
• Target Pathogen: Plasmodium spp.
• Target Disease: Malaria
• Type: Live, attenuated vaccine
• Status: Clinical trial
• Host Species for Licensed Use: Human
• Antigen: live (metabolically active), nonreplicating, radiation-attenuated P. falciparum sporozoites (SPZ)(Oneko et al., 2021)
• Immunization Route: Intravenous injection (i.v.)

Human Response

• Host Strain: Infants aged 5–12-month-old in Kenya(Oneko et al., 2021)
• Vaccination Protocol: Double-blind, randomized, placebo-controlled Phase2 trial.
  Participants were randomly assigned in 4 groups, each receiving 1) 4.5 × 105, 2) 9.0 × 105 and 3) 1.8 × 106 PfSPZ or 4) normal saline placebo. (Oneko et al., 2021)
• Immune Response: Dose-dependent increase in IgG and IgM antibody responses and a significantly greater rate of seroconversion and net increase in IgG and IgM antibodies: 94.0% and 89.5% of vaccinees and 12.7% and 12.7% of controls had increased IgG and IgM antibodies two weeks after third vaccination.
  Dose-dependent increase in the PfCSP-specific memory B cell response.
  ** There were low-to-undetectable PfSPZ-specific CD4 and CD8 T cell responses, which might because of the limited magnitude and functional capacity of γδ T cells in infants. (Oneko et al., 2021)
• Side Effects: Mild to moderate fever (more common in participants in the highest-dose group); febrile seizures. (Oneko et al., 2021)
• Efficacy: No statistically significant (P < 0.05) VE against the presence of parasitemia at the primary 6-month end point by either proportional or time-to-event analyses. (Oneko et al., 2021)

Human Response

• Host age: Adults(Seder et al., 2013)
• Vaccination Protocol: Phase I trial.
  57 adults participated in the trial. 40 of them were vaccine recipients (36 completed the vaccination), 12 were CHMI controls, and 5 were backup controls. For volunteers in the vaccination group: 1) 2 of the volunteers were given 2 × 10^3 PfSPZ per dose without CHMI to access safety, while the rest of the vaccination group were given 1.35 × 10^5 PfSPZ per dose and given CHMI later. (Seder et al., 2013)
• Challenge Protocol: CHMI ~3 weeks after last immunization (Seder et al., 2013)
• Efficacy: 16 of 17 subjects who received 7.5 × 10^3 and 3×10^4 PfSPZ Vaccine per dose developed parasitemia. Among the nine subjects who had received four doses of 3 × 10^4 PfSPZ Vaccine, one did not develop parasitemia, whereas the other eight had a 1.4 day prolongation of time to parasitemia compared with the six nonvaccinated controls (P = 0.007, LogRank). The prepatent periods in the 7.5 × 10^3 PfSPZ Vaccine-per-dose group were not significantly different than those of controls.
  12 of 15 subjects immunized with 1.35 × 10^5 PfSPZ Vaccine per dose were protected (P = 0.028). Three of nine subjects in the four-dose group and none of six in the five-dose group developed parasitemia (P = 0.015 for the fivedose group versus controls, Fisher’s exact test). All subjects who did not develop parasitemia were negative as determined by means of quantitative PCR at 28 days after CHMI. In the three vaccinated subjects that became infected, there was a modest delay in the time to positive PCR.
  (Seder et al., 2013)