A box of MMR vaccine (not reconstituted) was left at room temperature overnight. Can I use it?

Unfortunately, serious errors in vaccine storage and handling like this occur too often. If you suspect that vaccine has been mishandled, you should take the following steps: label the affected vaccine package clearly so it will not be used before knowing whether it is still usable, return the vaccine to recommended storage conditions, and then contact the manufacturer or state/local health department for guidance on whether it is still usable or should be wasted. This is particularly important for live virus vaccines like MMR and varicella.