It may not be just an age-related lack of immunity that explains the higher death rates among senior citizens in the novel coronavirus pandemic.

Some scholars are paying attention to the inverse correlation between the measles-mumps-rubella (MMR) vaccine coverage and COVID-19 fatality in their search for a possible deterrent against COVID-19 infection.

Among them is Professor Kook Hoon of Chonnam National University Hospital’s pediatrics department.

He says MMR vaccines could help mitigate the loss of lives before countries can achieve herd immunity with COVID-19 vaccines.  

“We cannot sit back and wait to receive the COVID-19 vaccination past the prioritized cohort. It would be a meaningful outcome if MMR vaccination, which is safe and affordable, could help reduce the spread of COVID-19 or deter the mild cases from progressing to severe,“ Kook told The Korea Herald.

Several researches have suggested the possibility of MMR vaccines as a deterrent against COVID-19.

According to an mBio article dated Nov. 20, 2020, a group of scientists headed by Jeffrey Gold showed that among 50 test candidates, those with asymptomatic and functionally immune COVID-19 cases had high mumps titer from MMR II vaccinations, while the moderate and severe cases of COVID-19 all had low mumps titer values.

As early as March 2020, Gold observed that recent, large-scale MMR vaccination campaigns were associated with the countries with the fewest COVID-19 deaths. Through his scientific pursuit, Gold is confident that there is a significant inverse correlation in mumps titer and COVID-19 severity. The inverse correlation was not age related, according to Gold.

In another study, dated April 10, Adam Young of Cambridge University identified similarities between the glycoprotein sequences in the SARS CoV-2 virus and the measles, mumps and rubella viruses -- 32 percent, 31 percent and 33 percent, respectively.

Further corroborating the claims is an article published by the New England Journal of Medicine dated Dec. 17, where researcher Matthew Kasper studies the case of US aircraft carrier vessel Theodore Roosevelt. In March, 1,271 of the 4,799 crew members (26.6 percent) on that ship tested positive for the coronavirus but only one died, leaving the mortality rate at merely 0.07 percent.

Only 23 (1.7 percent) required hospitalization and four (0.3 percent) needed intensive care.

According to researchers, those aboard the ship had received a fresh MMR vaccination at the time of their enlistment, regardless of their past vaccination history.

The MMR vaccine was introduced in the world for the first time in 1971, and was in use nationwide in 122 of World Health Organization’s member states as of the end of 2019.

According to WHO, In 2018, about 86 percent of the world’s children received one dose of measles vaccine by their first birthday through routine health services.

In the same year, 69 percent of children received the second dose of the measles vaccine.

Korea reported its first measles vaccination in 1983, and included the MMR vaccine in its national vaccination program from 2000. Between 2000 and 2001, a huge outbreak of measles rattled the nation, pushing the authorities to initiate a nationwide MMR vaccination for 580,000 students. The country gives two more MMR vaccinations for those who enlist in the military, at the time of their enlistment.

“Those who were born before the year 1980 in Korea, meaning Koreans above the age of 40, are unlikely to have received the state-sponsored MMR vaccination,” Kook said.

“And albeit a study dated 2014 states that 93.3 percent of those born between 1964 and 1974 have developed antibody against measles, the article by Gold offers that what may provide prevention against COVID-19 is the immunoglobulin G created from vaccination and not from natural infection,” Kook continued.

Kook said this would be a case of vaccine repurposing.

“Considering how it may take at least half a year for the country to distribute COVID-19 vaccines beyond the prioritized vulnerable cohort, a preliminary precaution may help alleviate the current situation,” he said.

For newborns, the MMR vaccine is administered twice -- the first being given within 12 months to 15 months after birth, and the second given between four and six years of age.

Adults who have never received the shot before are also suggested to take two doses given at least four weeks apart. 

The MMR vaccine is a live-attenuated vaccine, meaning it is made by removing disease-causing traits from a virus and leaving only its antigenicity to provoke an immune response in human body. Unlike natural infection, which can potentially lead to serious health repercussions, live-attenuated vaccine is a safe method to create immunity without a person having to catch the illness. The effects of both naturally created and vaccine-provoked antibody can diminish as time passes, however, and additional vaccination would help keep the body’s defense system up to date.

Korea sources its MMR vaccines from MSD Korea and GSK Korea. As of Wednesday, SK Bioscience has become a co-distributor of GSK’s MMR vaccine Priorix for adults.

In June, the Korea Disease Control and Prevention Agency had announced that it would store three months’ worth of the essential MMR and PPSV (pneumonia) vaccines, citing the global measles outbreak in 2019.

Kook reiterated that MMR vaccine could be an efficient solution to the circumstances the Korean government finds itself in, as the vaccine has 40 years' track record of global safety and minimal reported side effects.

Much would be elucidated, Kook said, once the ongoing phase 3 international clinical trial called Crown Coronation wraps up in August. The Crown Coronation, co-led by Washington University School of Medicine, University College London and the University of the Witwatersrand in Johannesburg, is testing the effects of MR or MMR vaccine for frontline healthcare workers fighting against COVID-19 cases. 

The trial is supported with funding by the COVID-19 Therapeutics Accelerator, which was launched by the Bill & Melinda Gates Foundation, Wellcome Trust and Mastercard.

By Lim Jeong-yeo (kaylalim@heraldcorp.com)