Covid-19: An MMR vaccine trial just started in SA - and latest research appears to be promising

• There's a chance the MMR vaccine may offer some protection against Covid-19 
• The finding is based on a recently published Mexican study, which studied 36 participants infected with Covid-19
• The researchers found that all participants who received the vaccine had only mild symptoms

While we await the outcome of clinical trials of Covid-19 vaccine candidates all over the world, existing vaccines could in the meantime help make the disease less deadly.

According to a recently published study, the mumps-measles-rubella (MMR) vaccine may help boost an individual’s immunity and even prevent Covid-19.

The research team was led by Dr Desiree Larenas-Linnemann from Medica Sur in Mexico City, which has been ranked as the leading hospital in the city since 2011.

Larenas-Linnemann and her team reported on their clinical observations of 255 volunteers who were vaccinated with the MMR vaccine at the start of the Covid-19 pandemic. Their findings were published in the September issue of Allergy, the European Journal of Allergy and Immunology.

Study resuts: Covid-19 cases all mild

For their study, researchers vaccinated 255 participants who were family members or caregivers of patients who had already contracted Covid-19, which meant they were already at extremely high risk of being infected.

A total of 36 of the participants ended up contracting Covid-19, but all with mild symptoms. Among the 36 participants, 13 were reported to have pre-existing conditions that are known to be a risk factor for severe disease. 

Only one patient had one day of mild low blood oxygen, but this was likely due to their uncontrolled asthma.  None of the participants experienced respiratory insufficiency to the point of needing oxygen.

The researchers also indicated that all participants had less severe symptoms than expected, given their health status and age. Age has been found to be a factor in Covid-19 disease severity and death, along with pre-existing health conditions such as hypertension and diabetes.

"We were relieved that MMR, which is commonly thought of as a childhood vaccination, seemed to help our older adult patients weather the storm too," said Larenas-Linnemann.

The team will be continuing their strategy to recommend MMR vaccination to household contacts of Covid-19 patients, and also plan on continuing data collection in further clinical cases.

Conclusive evidence of the efficacy and effectiveness of the MMR vaccine and other live attenuated vaccines against severe Covid-19, however, requires a randomised clinical trial, and this is something currently being investigated by microbiologist, Dr Paul Fidel of Louisiana State University.

Why they considered the MMR vaccine

The entire study came about as Larenas-Linnemann and her team were searching for methods to enhance innate immunity to give the body’s immune system a boost in order to prepare it for fighting off different pathogens.

However, considering Covid-19 is a new infectious disease, the team turned to the concept of "trained immunity”, also known as non-specific immunity. Essentially, this refers to the body’s enhanced immune response to a certain pathogen after being exposed – either via vaccination or natural illness – to another non-related pathogen.

When the body is exposed to this certain pathogen, the immune reaction is faster and mounts an increased production of certain cytokines (small proteins that signal the immune system to do its job).

In the context of this study, it means that some vaccinations may not only prevent the target disease, such as measles, but help the body fight other diseases as well. 

Larenas-Linnemann and her team therefore considered whether a live-attenuated vaccine could be protective against Covid-19. The timing was perfect, as the pandemic coincided with a rise in measles cases in Mexico, which led the Ministry of Health to recommend measles revaccination.

When this happened, it was the perfect opportunity for the researchers to test the effectiveness of trained immunity. 

Not the first study to test MMR vaccine against Covid-19

Earlier this week, Health24 reported on an SA trial that will test whether the MMR vaccine protects healthcare workers against Covid-19.