This vaccine may protect against worst symptoms of COVID-19

The MMR (measles, mumps, rubella) vaccine could serve as a preventive measure to dampen septic inflammation associated with COVID-19 infection, say researchers.

According to the study, published in the journal mBio, vaccination with MMR in immunocompetent individuals has no contraindications and may be especially effective for health care workers who can easily be exposed 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," said study researcher Paul Fidel from the Louisiana State University in the US.

"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," Fidel added.

The researchers said that mounting evidence demonstrates that live attenuated vaccines provide nonspecific protection against lethal infections unrelated to the target pathogen of the vaccine by inducing trained nonspecific innate immune cells for improved host responses against subsequent infections.

Live attenuated vaccines induce nonspecific effects representing "trained innate immunity" by training leukocyte (immune system cells) precursors in the bone marrow to function more effectively against broader infectious insults.

In Mairi Noverr's laboratory -- from Tulane University, in collaboration with Fidel, vaccination with a live attenuated fungal strain-induced trained innate protection against lethal polymicrobial sepsis.

The protection was mediated by long-lived myeloid-derived suppressor cells (MDSCs) previously reported inhibiting septic inflammation and mortality in several experimental models.

The researchers say that an MMR vaccine should be able to induce MDSCs that can inhibit or reduce the severe lung inflammation/sepsis associated with Covid-19.

Mortality in Covid-19 cases is strongly associated with progressive lung inflammation and eventual sepsis.Recent events provide support for the researchers' hypothesis.

The milder symptoms seen in the 955 sailors on the USS Roosevelt who tested positive for Covid-19 (only one hospitalisation) may have been a consequence of the fact that the MMR vaccinations are given to all US Navy recruits. In addition, epidemiological data suggest a correlation between people in geographical locations who routinely receive the MMR vaccine and reduced Covid-19 death rates.

The researchers propose a clinical trial to test whether the MMR vaccine can protect against COVID-19, but in the meantime, they suggest that all adults, especially health care workers and individuals in nursing homes get the MMR vaccine.