We did a randomised, controlled, phase IIb trial of RTS,S/AS02A given at 0, 1, and 2 months in 2022 Mozambican children aged 1–4 years. We previously determined vaccine ef
ficacy (VE) against clinical malaria in a double-blind phase that included study months 2·5–8·5 (VE
2·5–8·5). We now report VE in a single-blind phase up to month 21 (VE
8·5–21). The primary endpoint was time to
first or only clinical episode of
Plasmodium falciparum malaria (axillary temperature
37·5°C and
P falciparum asexual parasitaemia >2500 per μL) detected through a passive case detection system. We also determined VE for other case de
finitions and for episodes of severe malaria. This study is registered with the ClinicalTrials.gov identi
fier NCT00197041.
Findings
During the single-blind phase, VE(8·5–21) was 28·9%(95%CI 8·4–44·8; p=0·008). At month 21, prevalence of P falciparum infection was 29%lower in the RTS,S/AS02A group than in the control (p=0·017). Considering the entire study period, VE(2·5–21) was 35·3%(95%CI 21·6–46·6; p<0·0001) and VE(2·5–21) for severe malaria was 48·6%(95%CI 12·3–71·0; p=0·02).
Interpretation
These results show that RTS,S/AS02A confers partial protection in African children aged 1–4 years living in rural endemic areas against a range of clinical disease caused by P falciparum for at least 18 months, and confirm the potential of malaria vaccines to become credible control tools for public-health use.
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