Blood type paternity test back in the 90's?

Years ago before my husband and I were married, he had a relationship with a woman, that he thought that he could change. She cheated on him multiple times that he wasn’t aware. Anyway, he decided to get a blood test to rule out that he was the father. The test that he decided to go with was just a blood type test. The test came back that he was 97.851% that he was likely the father. He paid child support for this girl, but I have always wondered if it was accurate. We found out later that one of the other men had the same blood type as my husband. So, now I’m really wondering how accurate that test really was. Since this was such a long time ago and he has never had a relationship with this girl and we have a son together. Would it be worth it to get further testing done or is that blood type test really accurate?