The World Health Organisation has recommended the use of a second malaria vaccine to curb the life-threatening disease spread to humans by some mosquitoes.

"Almost exactly two years ago, WHO recommended the broad use of the world's first malaria vaccine called RTS,S," WHO chief Tedros Adhanom Ghebreyesus told a briefing in Geneva.

"Today, it gives me great pleasure to announce that WHO is recommending a second vaccine called R21/Matrix-M to prevent malaria in children at risk of the disease."

R21/Matrix-M, developed by the University of Oxford, will become available to countries by mid-2024, Tedros said, adding that doses would cost between $US2 and $US4 (between $A3.10 and $A6.30).

"WHO is now reviewing the vaccine for pre-qualification, which is WHO stamp of approval, and will enable GAVI (a global vaccine alliance) and UNICEF to buy the vaccine from manufacturers," Tedros said.

R21/Matrix-M is mass manufactured by Serum Institute of India and uses Novavax's Matrix M adjuvant.

Adar Poonawalla, CEO of Serum Institute of India, said it had already produced more than 20 million doses in anticipation of the WHO's recommendation.

"We will ramp it up as per what the demand requirements are," he told Reuters.

"We hope that by the end of 2024, there will be zero mismatch of demand and supply, with our supply coming into the system."

The vaccine will compete against the RTS,S shot by GSK plc, which was recommended by the United Nations agency in 2021 and sold under the brand Mosquirix.

The WHO said both vaccines had shown similar efficacy in separate trials but as there had been no head-to-head trial there was no evidence showing whether one performed better.

The agency has left it to countries to decide which product they will use based on various factors, including the affordability and supply.

"GSK has always recognised the need for a second malaria vaccine but it is increasingly evident that RTS,S, the first ever malaria vaccine and the first ever vaccine against a human parasite, set a strong benchmark," GSK said in a statement.

The company added that more than 1.7 million children in Ghana, Kenya and Malawi had received at least one dose of the shot and it would be rolled out in a further nine malaria endemic countries from early next year.

Tedros added the agency had also recommended Takeda Pharmaceuticals' vaccine against dengue called Qdenga for children aged six to 16 years living in areas where the infection is a significant public health problem.

Dengue, common in tropical and subtropical climates, is a viral infection spread from mosquitoes to people.

Takeda's vaccine was shown in trials to be effective against all four serotypes of the virus in people who were previously infected by dengue, Hanna Nohynek, chair of the WHO's Strategic Advisory Group of Experts on Immunisation, told journalists.

She added, however, that there remained uncertainty about its performance against serotype 3 and 4 in people who have not been infected previously.

The WHO's strategic advisory group also recommended a simplified single dose regime for primary immunisation for most COVID-19 vaccines to improve acceptance of the shots at a time when most people have had at least one prior infection.

The agency added that any monovalent or bivalent vaccine could be used given that monovalent vaccines that target the XBB.1.5 variant - the dominant variant in many places this year - are not available in many countries.