Rabies vaccination too soon

I go to petco to get my cats their rabies vaccines. Luv My Pet comes there every weekend and does them. In 2009 I went in January, so I assumed it was January 2010 that I went again, because I got a reminder in the mail saying my cat Lucas was due. I usually know when I took him because I usually get them done before he goes to his cat shows. He went to two last year, one in January and one in September. Well I took him in last weekend and they gave him a 3 year shot. I just today was looking through some things and found out he got his shot September 19, 2010. That's around 4 months ago. I'm scared to death he's going to get sick now, seeing as it was such a short time frame between the times he got his shots. Does anyone know anything about the effects of this? He was hiding for the first couple of days when we brought him home and not quite acting like himself, but he's usually like that after we get his shots. Thank you in advance.

Please consult a vet or go to the er if things do not get better ... Many many animals in shelter do get 2 shots in a year and are fine

As Jen said, shelters and rescues routinely have all strays vaccinated, so the number of cats inoculated twice without adverse effects is quite high. I wouldn't worry unless he actually seems sick.

At the shelter, we don't vaccinate for rabies, but we require any adopter to take them in for rabies shot within 2 weeks. We know that many of those cats were probably vaccinated more recently than 1 year, and we've never heard about any negative outcomes.

If you think he's acting sick, then bring him to the vet just incase, and tell them what happened.

Thanks for all the responses guys! He's acting himself again. He's seems to be fine but I'll be keeping a close eye on him.