If you accept "cognitive impairment" as a drop in IQ, then this meta study seems to find that globally after infection, and I claim my $5: https://pubmed.ncbi.

If you accept "cognitive impairment" as a drop in IQ, then this meta study seems to find that globally after infection, and I claim my $5: https://pubmed.ncbi.nlm.nih.gov/34973396/ https://pubmed.ncbi.nlm.nih.gov/34973396/ > A significant proportion of individuals experience persistent fatigue and/or cognitive impairment following resolution of acute COVID-19. > Ten studies analyzed data from Italy, nine from Spain, eight from the US, seven from China, six from the UK, three from Denmark, France, and Norway, respectively, two from Australia, Austria, Brazil, Canada, Egypt, Germany, Israel, Russia, and the Netherlands, respectively, and one from Belgium, the Czech Republic, England, Faroe Islands, Iran, Japan, Mexico, Pakistan, Singapore, Sweden, Switzerland, and Turkey, respectively...