Answer : 3. "Malaria"
Explanation :

The World Health Organization (WHO) has recommended a new vaccine, R21/Matrix-M, for the prevention of malaria in children. It has been jointly developed by Oxford University and Serum Institute of India (SII). The R21 vaccine is the second malaria vaccine recommended by the WHO after the RTS,S/AS01 vaccine, which received the WHO recommendation in 2021. Both vaccines are said to be safe and effective in preventing malaria in children.