Live attenuated vaccines may prevent lung inflammation and sepsis associated with COVID-19

Reviewed by Emily Henderson, B.Sc.Jun 26 2020

A paper published by Paul Fidel, Jr., PhD, Professor and Director of the Center of Excellence in Oral and Craniofacial Biology and Associate Dean for Research at LSU Health New Orleans School of Dentistry, and Mairi Noverr, PhD, Professor of Microbiology & Immunology at Tulane University School of Medicine in New Orleans, suggests that live attenuated vaccines such as MMR (measles, mumps and rubella) may prevent the severe lung inflammation and sepsis associated with COVID-19 infection.

The paper was published online in mBio Increasing evidence demonstrates that live attenuated vaccines can activate nonspecific immune cells to train leukocytes (the white blood cells of the immune system) to mount a more effective defense against unrelated infections. The researchers demonstrated in a laboratory that vaccination with a live attenuated fungal strain generated trained innate protection against lethal sepsis (blood poisoning) caused by a combination of disease-causing fungi and bacteria.

The authors propose that the protection from an unrelated live attenuated vaccine is produced by long-lived myeloid-derived suppressor cells (MDSCs) previously reported to inhibit septic inflammation and mortality in several experimental models. They stress that this live attenuated MMR vaccine concept is NOT in any way suggested to be directed against COVID-19, but instead an immune preventive measure against the severe inflammatory symptoms of COVID-19.

The use of childhood live attenuated vaccines such as MMR given to adults to induce bystander cells that can dampen or reduce severe complications associated with COVID-19 infection is a low risk - high reward preventive measure during a critical period of the pandemic. These bystander cells are long-lived but not life-long. Anyone who had an MMR vaccination as a child, while likely to still have immune antibodies directed against measles, mumps, or rubella, will not likely still have the immune cells directed against sepsis. So, it could be important to get the MMR vaccination as an adult to protect better against COVID-related sepsis."

Paul Fidel, Jr., Ph.D., Professor and Director of the Center of Excellence in Oral and Craniofacial Biology and Associate Dean for Research at LSU Health New Orleans School of Dentistry

A similar concept is being tested in other countries. The authors write "at least six clinical trials have been initiated in Europe, Australia, and the United States to test vaccination with Mycobacterium bovis BCG (live attenuated tuberculosis [TB] vaccine) or placebo in high-risk health care workers to determine whether beneficial trained innate responses against COVID-19 can be elicited."

In contrast, Fidel and Noverr propose that the trained innate response includes induction of the MDSCs that can inhibit/reduce the severe lung inflammation/sepsis associated with COVID-19.

"While we initiate the clinical trials and animal model studies to test the hypothesis that the MMR vaccine given to adults induces the bystander cells that we propose can inhibit the severe lung inflammation/sepsis associated with COVID-19 infection, we suggest adults working in high-risk settings who are not immunocompromised, pregnant or allergic to vaccinations, get an MMR vaccine/booster," Fidel concludes. "If we're correct, an MMR-vaccinated person may suffer less if infected with COVID-19. If we're wrong, the person has better immunity to measles, mumps, and rubella. A sort of no harm no foul action."