What is the efficacy of the malaria vaccine, specifically RTS,S (Recombinant Target Antigen), in preventing malaria?

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Last updated: November 17, 2025 • View editorial policy

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Malaria Vaccine Efficacy

The RTS,S/AS01 malaria vaccine demonstrates moderate efficacy, preventing approximately 36% of clinical malaria cases in children aged 5-17 months and 26% in infants aged 6-12 weeks over 3-4 years, with substantially higher protection against severe malaria (32% in children), making it a valuable but partial tool that must be combined with chemoprophylaxis and mosquito avoidance measures. 1

Efficacy by Age Category

Children (5-17 months at vaccination)

  • Vaccine efficacy against clinical malaria: 36.3% (95% CI 31.8-40.5%) over 48 months when administered with a booster dose at month 20 1
  • Without booster: 28.3% efficacy (95% CI 23.3-32.9%) 1
  • Protection against severe malaria: 32.2% (95% CI 13.7-46.9%) with booster 1
  • Cases averted: 1,774 clinical malaria episodes per 1,000 children vaccinated with booster regimen 1

Infants (6-12 weeks at vaccination)

  • Vaccine efficacy against clinical malaria: 25.9% (95% CI 19.9-31.5%) over 38 months with booster 1
  • Without booster: 18.3% efficacy (95% CI 11.7-24.4%) 1
  • No significant protection against severe malaria in this age group 2, 1
  • Cases averted: 983 clinical malaria episodes per 1,000 infants vaccinated with booster 1

Critical Factors Affecting Efficacy

Transmission Intensity

Efficacy varies dramatically by malaria transmission intensity, creating a paradox where the vaccine works best in areas with lower disease burden 3:

  • Low transmission (parasite prevalence 10%): 60% efficacy (95% CI 54-67%) 3
  • Moderate transmission (parasite prevalence 20%): 41% efficacy (95% CI 21-57%) 3
  • High transmission (parasite prevalence 70%): 4% efficacy (95% CI -10 to 22%) 3

Waning Immunity

Protection decreases substantially over time, requiring booster doses 3:

  • At vaccination: 36% efficacy (95% CI 24-45%) 3
  • After 3 years: 0% efficacy (95% CI -38 to 38%) 3
  • The booster dose at month 20 significantly enhances protection in both age categories 1

Adjuvant Selection

AS01 adjuvant demonstrates superior efficacy compared to AS02 3:

  • AS01 at low transmission: 60% efficacy (95% CI 54-67%) 3
  • AS02 at low transmission: 47% efficacy (95% CI 14-75%) 3

Real-World Impact

Number of Cases Prevented

The absolute number of cases averted varies dramatically by transmission intensity 2:

  • Children: 37 to 2,365 clinical malaria cases averted per 1,000 vaccinated across different sites 2
  • Infants: -10 to 1,402 clinical malaria cases averted per 1,000 vaccinated 2
  • Severe malaria cases averted in children: -1 to 49 per 1,000 vaccinated 2

Safety Considerations

Meningitis was reported more frequently in vaccinated groups: 21 cases in RTS,S/AS01 recipients versus 1 case in controls among children, and 12 cases versus 3 cases among infants 2, 1

Generalized convulsive seizures within 7 days of booster: 2.2 per 1,000 doses in infants and 2.5 per 1,000 doses in children 1

Integration with Existing Malaria Prevention

The vaccine cannot replace chemoprophylaxis or mosquito avoidance measures 4:

  • No chemoprophylactic regimen provides 100% protection, and the same applies to vaccination 4
  • Mosquito avoidance remains essential: DEET-containing repellents, permethrin-treated bed nets, and protective clothing after sunset 4
  • Chemoprophylaxis is still required for travelers to endemic areas, with drug selection based on resistance patterns 4

Clinical Bottom Line

RTS,S/AS01 provides meaningful but incomplete protection, particularly in children aged 5-17 months in areas of moderate transmission intensity 1. The vaccine's efficacy is highest when combined with a booster dose and is most effective in preventing severe disease rather than all clinical episodes 1. Healthcare providers must counsel that vaccination does not eliminate the need for chemoprophylaxis in travelers or for mosquito avoidance measures in endemic populations 4. The vaccine represents an important addition to malaria control strategies but functions as one component of a comprehensive prevention approach rather than a standalone solution 1.

References

4
Guideline

Malaria Prophylaxis Medication Options

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2025

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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