Live attenuated vaccines sometimes are effective beyond the providing immunity for the targeted pathogen, according to a new study. That’s why the authors suggest that the measles, mumps, rubella (MMR) vaccine might help reduce septic inflammation associated with COVID-19 infection.  

An article in mBio, a journal of the American Society for Microbiology, suggests that could be the case. 

The co-authors—spouses Paul Fidel, Jr., PhD, of Louisiana State University Health School of Dentistry and Mairi Noverr, PhD, of Tulane University School of Medicine, both in New Orleans—wrote a perspective article on the topic. 

The authors emphasize that vaccination with MMR in immunocompetent individuals has no contraindications and might be especially effective for healthcare workers who are at risk of exposure to COVID-19. 

“Live attenuated vaccines seemingly have some nonspecific benefits as well as immunity to the target pathogen. A clinical trial with MMR in high-risk populations may provide a low-risk-high-reward preventive measure in saving lives during the COVID-19 pandemic," Dr. Fidel points out, “While we are conducting the clinical trials, I don't think it's going to hurt anybody to have an MMR vaccine that would protect against the measles, mumps, and rubella with this potential added benefit of helping against COVID-19.” 

In an experiment, the authors demonstrated that vaccination with a live attenuated fungal strain induced trained innate protection against lethal polymicrobial sepsis. They explain that the protection was mediated by long-lived myeloid-derived suppressor cells (MDSCs) previously reported to inhibit septic inflammation and mortality in several experimental models. The researchers posit that an MMR vaccine should be able to induce MDSCs to reduce the severe lung inflammation/sepsis that is associated with COVID-19 and is strongly associated with mortality in the infection. 

Drs. Fidel and Noverr raise the possibility, for example, that milder symptoms among 955 sailors on the U.S.S Roosevelt who tested positive for COVID-19—which led to only one hospitalization—might have been a result of universal MMR vaccination of Navy recruits. They add that epidemiological data suggests a correlation between people in geographical locations routinely receiving the MMR vaccine and reduced COVID-19 death rates.  

COVID-19’s lesser impact on children also is an issue, according to the authors, possibly because of their more recent exposure to live attenuated vaccines that can also induce the trained suppressive MDSCs that limit inflammation and sepsis. The researchers propose a clinical trial to test whether the MMR vaccine can protect against COVID-19, but also urge that adults, especially healthcare workers and individuals in nursing homes, get the MMR vaccine. 

“If adults got the MMR as a child, they likely still have some level of antibodies against measles, mumps, and rubella, but probably not the myeloid-derived suppressor cells,” Dr. Fidel emphasizes. “While the MDSCs are long-lived, they are not life-long cells. So, a booster MMR would enhance the antibodies to measles, mumps, and rubella and reinitiate the MDSCs. We would hope that the MDSCs induced by the MMR would have a fairly good life-span to get through the critical time of the pandemic.” 

“Following the lead of other countries conducting clinical trials with the live attenuated Mycobacterium bovis BCG (BCG) vaccine under a similar concept, a clinical trial with MMR in high-risk populations may provide a ‘low-risk–high-reward’ preventive measure in saving lives during this unprecedented COVID-19 pandemic,” the authors write.

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