GMAT Verbal Section | Re: Is its a plural pronoun?

Hello All and specially experts

I have a question regarding the usage of the possessive pronouns its, which refers to recipients mentioned in the quoted para below: Since the word its refers to recipients, shouldn't it be a plural possessive pronoun like their or its refers to each recipient instead?

"Since the first successful transplant was performed in the United States in the 1954, a series problem faced by transplantrecipients has been the possibilities thatits own body will try