Probably India if it is anywhere. They use a killed vaccine. Forgot the name of the magnate that owns all the horses they use to make it. He started out with racing horses but found more money in using them to make vaccines. I know one person that made two trips to India to get vaccinated somewhere near Agra and went to see the Taj when he was there.
Very possible. India saved 300 million from the flu using ivermectin and a concoction of great stuff from D3 to C to Zinc,they were way ahead of everyone.