According to an official statement from Slovakian MOD, they were replaced with 4 batteries of Patriot SAMs:There goes one of the few kind of working air defense systems NATO has in Eastern Europe. Oops.
Security of the Slovak Republic and our citizens is our highest priority. That is why we decided to make this decision in the moment, when we have the adequate replacement for the S-300 system, as we had stated before. Fourth battery of the Patriot system, one of the most modern air-defence systems, provided by our Allies, will be deployed in Slovakia. Together, four batteries of the Patriot system will cover the territory of the Slovak Republic. Due to the technical condition, limited options of maintenance and age of the S-300 system, the deployment of the fourth battery of the Patriot system is great news for Slovakia and at the same time tremendous help for Ukraine.”