one of the barriers to vaccination is the amount of fake news circulating in the community. there is a lot of fake news deliberately created by irresponsible people so that people are afraid to receive vaccines. maybe this is what is happening in Russia right now, and of course it is also happening in many other countries.
In Russia, there is widespread opposition to the government and in general there is a lot of distrust with the authorities. And this distrust didn't appeared all of a sudden. It has been there since the 1920s, when the communists came to power. After the fall of communism, the regimes that succeeded the communists were even worse (Yeltsin first, and then Putin).