Patients who have been vaccinated for MMR, measles-mumps-rubella, would be better protected against severe forms of coronavirus infection.
- The researchers were interested in the concept of immune memory, that is to say the immunity reinforced by exposure, whether by vaccination or natural disease, to another unrelated pathogen.
- None of the vaccinated people who contracted Covid-19 developed a serious form.
What if an existing vaccine could make Covid-19 less deadly? An observational study shows promising results for the MMR vaccine, for measles-mumps-rubella. Produced by Mexican researchers, it was published on September 7 in the journal allergy, the European Journal of Allergy and Immunology. For this study, the researchers observed 255 patients already vaccinated against MMR and who are family members or caregivers of patients who have already contracted Covid-19. Among them, 36 were infected with Covid-19. None of them developed a serious form despite their state of health and their age.
Immune memory
The researchers were interested in the concept of immune memory, that is to say the immunity reinforced by exposure, whether by vaccination or natural disease, to another unrelated pathogen. This means that certain vaccinations can not only prevent the targeted disease but also help people fight other diseases. Taking advantage of the fact that the coronavirus pandemic in Mexico coincided with an increase in measles cases, the team of researchers decided to study this concept of immune memory for people who had been vaccinated against measles. They gave their patients booster shots of a standard childhood vaccine, measles-mumps-rubella (MMR).
Researchers rated the clinical severity of infections on a simplified scale from zero for asymptomatic cases, to 1 for mild cases, 2 for moderate, 3 for lower respiratory tract symptoms without the need for oxygen, up to 6 for deaths. They also performed home pulse oximetry and peak expiratory flow (PEFR) measurements to determine severity. Of the 255 people vaccinated, there have been 24 confirmed cases, and 12 highly probable cases, including thirteen with risk factors that can often make Covid-19 more serious (hypertension, diabetes, obesity, smoking or uncontrolled asthma).
BCG also under study
All infected patients were less severe cases than expected. At most, some developed minor respiratory symptoms. None of the 36 cases required supplemental oxygen. “We were relieved to see that the MMR vaccine, which is generally considered a childhood vaccination, seems to be helping our older adult patients weather the coronavirus storm as well.”, rejoiced Dr. Larenas-Linnemann who works at the Medica Sur hospital in Mexico City and led the study.
MMR is not the only vaccine on the bench to prevent serious complications from Covid-19. Several clinical trials are currently underway on tuberculosis (BCG) vaccination. Mexican researchers noted that one of the effects described in BCG-induced immunity experiments, an increase in the cytokine of interleukin, led them to be reluctant to use this vaccine in an attempt to prevent serious forms. Dr. Larenas-Linnemann’s team opted for the MMR vaccine for its safety profile. Additionally, previous research has described trained immunity to MMR in newborns of hepatitis-infected mothers. Previous studies have shown a 26-49% decrease in mortality rates after the measles vaccination program.
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