Yes they are! But only if you have monthly or yearly lenses.
Some lenses are meant for 1 use, then you throw them away. Others are meant to last for many uses between 1 and 12 months, assuming you care for them properly.
Check the packaging of your lenses, it should be stated clearly how long they last, if you see yearly, monthly then you can wear more than once. If you see the word Daily, this means they're meant to be thrown away after 1 use.
So it really depends on the product you have, Halloween Contact Lenses from Camo Eyes last 1 year and you can wear them many times, other brands might be selling cheaper products that only last for 1 use or at most 1 month.