Hello,
Since your 2nd dose of vaccine would be your 3rd exposure to the virus, your body may react more strongly (fever, chills, muscle aches, fatigue, diarrhea, vomiting, etc.) and for a longer period of time (about 48-72 hours). However, there is no greater risk of a severe reaction.
Generally, when one is immunosuppressed, the immune system is less responsive to vaccines than an immunocompetent person. Therefore, it is generally recommended to receive a 2nd dose of vaccine even if one has been infected with COVID-19.
If you are immunocompetent, like your spouse, the second dose does not provide additional immunity and may cause side effects as mentioned above. However, if he wants to receive his 2nd dose, the vaccination center staff cannot refuse to vaccinate him. He can receive his dose anyway.
I hope this answers your question,
Sandrine