Is it right to request someone who is sick to not come to Thanksgiving?

My SO’s sister’s 14 month old daughter has pneumonia and she’s decided to go to Thanksgiving. I’m 33 weeks pregnant and there are multiple older family members who do NOT need to potentially catch pneumonia, imo.

Their family is super religious, doesn’t believe in vaccines (none of them are vaccinated), and they don’t believe that pneumonia is contagious.

So..is it right to request that that person not go? This is VERY controversial for his side of the family as they believe in putting it in “God’s hands”... sorry if this doesn’t belong here!