An experimental malaria vaccine protected healthy adults from infection for more than a year in a clinical trial in US, an advance that may help control and ultimately eradicate the deadly disease.
Researchers at the University of Maryland conducted the clinical evaluation of the vaccine, which involved immunisation and exposing adults to the malaria-causing parasite Plasmodium falciparum (P falciparum).
The PfSPZ Vaccine, is composed of live, but weakened P falciparum sporozoites – the early developmental form of the parasite.
Previous research showed the PfSPZ Vaccine to be highly protective three weeks after immunisation. In this trial, researchers assessed if protection could last for five months to a year.
“Malaria remains one of the most devastating diseases in the world, especially among young children in Africa,” said Anthony S Fauci, director of the US National Institute of Allergy and Infectious Diseases (NIAID).
“A malaria vaccine that provides long-term protection is urgently needed to reduce mortality and eliminate transmission. This study is an encouraging step forward in our goal to control and ultimately eradicate malaria,” Fauci said.
The Phase 1 trial enrolled 101 healthy adults aged 18 to 45 years who had never had malaria. Of these volunteers, 59 received the PfSPZ Vaccine; 32 participants served as controls and were not vaccinated.
Vaccine recipients were divided into several groups to assess the roles of the route of administration, dose, and number of immunisations in conferring short- and long-term protection against malaria.
The results showed that the PfSPZ Vaccine provided malaria protection for more than one year in 55 per cent of people without prior malaria infection.
In those individuals, the PfSPZ Vaccine appeared to confer sterile protection, meaning the individuals would be protected against disease and could not further transmit malaria. The vaccinations were also well-tolerated among participants, and there were no serious adverse events attributed to vaccination.
Additional results showed that antibodies may play a role in malaria protection early after the final immunisation, but inducing T cells in the liver is likely necessary for durable protection.
“It is now clear that administering the PfSPZ Vaccine intravenously confers long-term, sterile protection in a small number of participants, which has not been achieved with other current vaccine approaches,” said Robert A Seder, from NIAID.
Long-term, reliable protection is important for people who are vaccinated but not exposed to malaria for months, such as travellers and military personnel, researchers said. The study was published in the journal Nature Medicine.