A major breakthrough in the fight against malaria has been made with the introduction of the RTS, S, and R21 vaccines. Through targeting the same protein on malaria parasites, both vaccinations could significantly lower the number of child malaria cases and fatalities.
Because studies and circumstances fluctuate, it can be difficult to interpret vaccine effectiveness estimates because of changes in immunisation techniques, follow-up times, and malaria transmission levels.
Research shows that a seasonal strategy optimises effectiveness; nevertheless, compared to age-based methods, seasonal vaccination requires more work to execute. While the R21 results are based on a mere 12-month period, the RTS, S trials have yielded data spanning seven years.
Vaccine Efficacy
– RTS,S: The phase 3 trial conducted from 2009 to 2014 showed a 51% reduction in malaria cases during the year following vaccination. The seasonal strategy, with three doses before the rainy season and annual boosters, showed a 72% efficacy during the first year.
– R21: Trials since 2019 have shown that R21 reduces clinical malaria by 66% when administered using an age-based approach. The seasonal approach reduced cases by 75% during the first year.
Seasonal vaccination is more complicated to administer than age-based immunisation, although both vaccinations are more effective during the malaria season.
Transmission Intensity and Impact
The efficacy percentages in low-transmission regions are higher, according to the results, while the vaccinations work better in high-transmission locations. Since both vaccines target parasites during their first stage of liver growth, none provides total protection.
Duration of Protection
RTS,S shows a gradual decrease in protection over time, similar to other vaccines like those for COVID-19. Children continue to benefit from RTS,S vaccination over seven years. The duration of protection for R21 is not yet fully known, as trials are still ongoing.
Public Health Results
Pilot implementations of RTS,S have demonstrated a notable reduction in severe malaria and a 13% decrease in deaths among vaccinated children in Ghana, Kenya, and Malawi from 2019 to 2023. Data for R21 does not yet fully assess its impact on severe malaria and mortality.
Source: Gavi
