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Photo by Caitlin Kleiboer
Results of a phase 2 trial suggest that changing the dosing schedule can improve the efficacy of the malaria vaccine candidate RTS,S/AS01 (Mosquirix).
Researchers tested RTS,S/AS01 in 46 malaria-naïve US adults, using the controlled human malaria infection model (CHMI).
About 87% of subjects who received the modified dosing regimen were protected from malaria, compared to 63% of subjects who received the standard dosing schedule.
Jason Regules, MD, of the US Army Medical Research Institute of Infectious Diseases in Frederick, Maryland, and his colleagues reported these results in the Journal of Infectious Diseases.
The study was funded by GlaxoSmithKline, the US Military Infectious Disease Research Program, and the PATH Malaria Vaccine Initiative. RTS,S/AS01 is being developed by GlaxoSmithKline and the PATH Malaria Vaccine Initiative.
RTS,S/AS01 has been tested in trials of young children in Africa, and early results seemed promising. But long-term follow-up in a phase 2 study and a phase 3 study suggested the vaccine’s efficacy wanes over time.
Therefore, Dr Regules and his colleagues sought to determine if a novel immunization schedule—specifically, delaying RTS,S/AS01 administration and reducing dosage of the third vaccination, as well as any following booster dose—would significantly increase the vaccine’s ability to protect against infection.
The researchers evaluated RTS,S/AS01 in 46 malaria-naïve adults. First, the team immunized the subjects according to 2 regimens:
- A 0-, 1-, 7-month schedule with a fractional third dose (Fx017M)
- A 0-, 1-, 2-month schedule (012M, the current standard).
Following the third vaccination, subjects were exposed to malaria-causing parasites using CHMI, and the researchers evaluated the extent to which each regimen protected against infection.
During follow-up, the team assessed the efficacy of an additional fractional dose, or booster, in protecting against a second CHMI.
Twenty-six of the 30 subjects—86.7%—who received the Fx017M regimen and 10 of the 16—62.5%—who received the 012M regimen were protected from infection following the first CHMI.
In addition to providing more protection from malaria infection, the Fx017M regimen delayed infection longer than the 012M regimen.
About 90% of the Fx017M group who received a fourth fractional booster dose and underwent the second CHMI were protected from infection.
Four out of 5 subjects from both vaccination groups who were infected during the first CHMI were protected against the second, after receiving the fourth (fractional) dose of RTS,S/AS01.
The subjects did not report any serious health events as a result of receiving the vaccinations, and no safety concerns were associated with reducing dosages.
“With these results in hand, we are planning additional studies in the United States and Africa that will seek to further refine the dosing and schedule for maximum impact and to see whether these early stage results in American adults will translate into similarly high efficacy in sub-Saharan Africa, a region that bears much of the malaria disease burden,” said study author Ashley J. Birkett, PhD, director of PATH’s Malaria Vaccine Initiative.
“The results of these planned studies won’t be available for several years, however. It therefore remains critical that the pilot implementation for the recommended pediatric regimen of RTS,S/AS01, being led by the World Health Organization, moves forward as soon as possible. We need to help protect as many children as we can, as soon as we can, while we continue to pursue eradication—the only truly sustainable solution to malaria.” 
Photo by Caitlin Kleiboer
Results of a phase 2 trial suggest that changing the dosing schedule can improve the efficacy of the malaria vaccine candidate RTS,S/AS01 (Mosquirix).
Researchers tested RTS,S/AS01 in 46 malaria-naïve US adults, using the controlled human malaria infection model (CHMI).
About 87% of subjects who received the modified dosing regimen were protected from malaria, compared to 63% of subjects who received the standard dosing schedule.
Jason Regules, MD, of the US Army Medical Research Institute of Infectious Diseases in Frederick, Maryland, and his colleagues reported these results in the Journal of Infectious Diseases.
The study was funded by GlaxoSmithKline, the US Military Infectious Disease Research Program, and the PATH Malaria Vaccine Initiative. RTS,S/AS01 is being developed by GlaxoSmithKline and the PATH Malaria Vaccine Initiative.
RTS,S/AS01 has been tested in trials of young children in Africa, and early results seemed promising. But long-term follow-up in a phase 2 study and a phase 3 study suggested the vaccine’s efficacy wanes over time.
Therefore, Dr Regules and his colleagues sought to determine if a novel immunization schedule—specifically, delaying RTS,S/AS01 administration and reducing dosage of the third vaccination, as well as any following booster dose—would significantly increase the vaccine’s ability to protect against infection.
The researchers evaluated RTS,S/AS01 in 46 malaria-naïve adults. First, the team immunized the subjects according to 2 regimens:
- A 0-, 1-, 7-month schedule with a fractional third dose (Fx017M)
- A 0-, 1-, 2-month schedule (012M, the current standard).
Following the third vaccination, subjects were exposed to malaria-causing parasites using CHMI, and the researchers evaluated the extent to which each regimen protected against infection.
During follow-up, the team assessed the efficacy of an additional fractional dose, or booster, in protecting against a second CHMI.
Twenty-six of the 30 subjects—86.7%—who received the Fx017M regimen and 10 of the 16—62.5%—who received the 012M regimen were protected from infection following the first CHMI.
In addition to providing more protection from malaria infection, the Fx017M regimen delayed infection longer than the 012M regimen.
About 90% of the Fx017M group who received a fourth fractional booster dose and underwent the second CHMI were protected from infection.
Four out of 5 subjects from both vaccination groups who were infected during the first CHMI were protected against the second, after receiving the fourth (fractional) dose of RTS,S/AS01.
The subjects did not report any serious health events as a result of receiving the vaccinations, and no safety concerns were associated with reducing dosages.
“With these results in hand, we are planning additional studies in the United States and Africa that will seek to further refine the dosing and schedule for maximum impact and to see whether these early stage results in American adults will translate into similarly high efficacy in sub-Saharan Africa, a region that bears much of the malaria disease burden,” said study author Ashley J. Birkett, PhD, director of PATH’s Malaria Vaccine Initiative.
“The results of these planned studies won’t be available for several years, however. It therefore remains critical that the pilot implementation for the recommended pediatric regimen of RTS,S/AS01, being led by the World Health Organization, moves forward as soon as possible. We need to help protect as many children as we can, as soon as we can, while we continue to pursue eradication—the only truly sustainable solution to malaria.”
Photo by Caitlin Kleiboer
Results of a phase 2 trial suggest that changing the dosing schedule can improve the efficacy of the malaria vaccine candidate RTS,S/AS01 (Mosquirix).
Researchers tested RTS,S/AS01 in 46 malaria-naïve US adults, using the controlled human malaria infection model (CHMI).
About 87% of subjects who received the modified dosing regimen were protected from malaria, compared to 63% of subjects who received the standard dosing schedule.
Jason Regules, MD, of the US Army Medical Research Institute of Infectious Diseases in Frederick, Maryland, and his colleagues reported these results in the Journal of Infectious Diseases.
The study was funded by GlaxoSmithKline, the US Military Infectious Disease Research Program, and the PATH Malaria Vaccine Initiative. RTS,S/AS01 is being developed by GlaxoSmithKline and the PATH Malaria Vaccine Initiative.
RTS,S/AS01 has been tested in trials of young children in Africa, and early results seemed promising. But long-term follow-up in a phase 2 study and a phase 3 study suggested the vaccine’s efficacy wanes over time.
Therefore, Dr Regules and his colleagues sought to determine if a novel immunization schedule—specifically, delaying RTS,S/AS01 administration and reducing dosage of the third vaccination, as well as any following booster dose—would significantly increase the vaccine’s ability to protect against infection.
The researchers evaluated RTS,S/AS01 in 46 malaria-naïve adults. First, the team immunized the subjects according to 2 regimens:
- A 0-, 1-, 7-month schedule with a fractional third dose (Fx017M)
- A 0-, 1-, 2-month schedule (012M, the current standard).
Following the third vaccination, subjects were exposed to malaria-causing parasites using CHMI, and the researchers evaluated the extent to which each regimen protected against infection.
During follow-up, the team assessed the efficacy of an additional fractional dose, or booster, in protecting against a second CHMI.
Twenty-six of the 30 subjects—86.7%—who received the Fx017M regimen and 10 of the 16—62.5%—who received the 012M regimen were protected from infection following the first CHMI.
In addition to providing more protection from malaria infection, the Fx017M regimen delayed infection longer than the 012M regimen.
About 90% of the Fx017M group who received a fourth fractional booster dose and underwent the second CHMI were protected from infection.
Four out of 5 subjects from both vaccination groups who were infected during the first CHMI were protected against the second, after receiving the fourth (fractional) dose of RTS,S/AS01.
The subjects did not report any serious health events as a result of receiving the vaccinations, and no safety concerns were associated with reducing dosages.
“With these results in hand, we are planning additional studies in the United States and Africa that will seek to further refine the dosing and schedule for maximum impact and to see whether these early stage results in American adults will translate into similarly high efficacy in sub-Saharan Africa, a region that bears much of the malaria disease burden,” said study author Ashley J. Birkett, PhD, director of PATH’s Malaria Vaccine Initiative.
“The results of these planned studies won’t be available for several years, however. It therefore remains critical that the pilot implementation for the recommended pediatric regimen of RTS,S/AS01, being led by the World Health Organization, moves forward as soon as possible. We need to help protect as many children as we can, as soon as we can, while we continue to pursue eradication—the only truly sustainable solution to malaria.”