There has been some anecdotal data showing that live virus vaccines (like measles/mumps/rubella - also called 'MMR' - and intranasal flu) may impact a person's likelihood of getting COVID-19 or how serious their infection is. Researchers studied the level of immunity to MMR diseases in the blood of COVID patients. They found that the higher a person's antibodies to mumps, the less likely they are to experience serious COVID-19 illness. This finding of an inverse correlation applied to people under 42 years old vaccinated with the MMR II vaccine produced by Merck. The lead author stated, "[...] the MMR vaccine may be protective against COVID-19. It also may explain why children have a much lower COVID-19 case rate than adults, as well as a much lower death rate." People who had no history of vaccination, or who had mumps earlier in their lives, did not see the same decreased severity in their COVID-19 infections.