Mixing experimental vaccines for global killer shows amazing results

19 Jun 2018

Image: corlaffra/Shutterstock

For the first time, the combination of two experimental vaccines has shown to significantly improve effectiveness in one of the world’s most deadly parasites, malaria.

It would be pretty reasonable to assume that combining two different vaccines into one is an idea too simple to prove effective, but a team from Imperial College London (ICL) has confirmed the process has produced astounding results for the prevention of malaria.

With nearly half of the world’s population at risk from infection through mosquitoes, roughly 212m cases and an estimated 429,000 malaria deaths occurred in 2015, making it one of the world’s biggest killer parasites, according to the World Health Organization (WHO).

The ICL team has published findings in the journal eLife showing that combining two experimental vaccines – each of which achieves prevention in 48pc and 68pc of cases, respectively – can return prevention results as high as 91pc.

Each of the vaccines are at different stages of human trials and, until now, had not been combined. They were selected based on them being two different types.

The first type, called transmission-blocking vaccines (TBVs), prevents mosquitoes from transferring the parasites; while the second type prevents the parasite from infecting the liver, termed pre-erythrocytic vaccines (PEVs).

Under our nose the whole time

Currently, the most popular PEV malaria vaccine is one called ‘RTS,S’ and has been shown to provide partial protection against malaria in young children by blocking infection of the liver, but its maximum efficacy is under 50pc.

However, several types of TBVs are currently undergoing early trials that reduce the number of parasites in mosquito salivary glands with a maximum efficacy of between 50pc and 95pc.

Until now, despite it being considered as beneficial in treatment, combining these types of vaccines had never been attempted but has now proven to be very effective.

The team also found that combining any of the two types of vaccines improved efficacy of the mixture more than might be expected from the single efficacy of each vaccine separately.

“While these findings are in the preliminary stages, they’re valuable as they shed light on optimising strategies for preventing malaria,” said Dr Morven Roberts, programme manager for parasites and neglected tropical diseases at ICL’s Medical Research Council.

“Learning that combining vaccines can dramatically boost efficacy in mice provides another potential tactic for controlling this disease. This is timely research as global health officials work towards WHO targets to eliminate malaria by 2030.”

The plan now is to see how combined vaccines could work in more complex situations through rodent experiments and computer modelling.

Updated, 2.41pm, 19 June 2018: This article has been amended to clarify that malaria is a parasite, not a virus. 

Colm Gorey was a senior journalist with Silicon Republic