Answer : 1. "Bulgaria"
Explanation :

Nigeria is at the forefront of the global fight against meningitis, having introduced the unprecedented Men5CV vaccine, supported by WHO, which targets five strains at once. This has overtaken previous vaccines, which is important as bacterial meningitis, prevalent in Africa, poses serious health risks. Cases are increasing in Africa's “meningitis belt,” including Nigeria, which reported a 50% increase last year. Nigeria's pioneering step sets a precedent for widespread adoption around the world, marking a significant advance in public health.