Even experts are shocked by the remarkable success of the two first messenger RNA vaccines developed by Moderna and Pfizer/BioNTech against COVID-19.

"If you told me before that these vaccines are 95% effective, I would say you were dreaming," said Andrew Pekosz, a professor in the Department of Molecular Microbiology and Immunology at Johns Hopkins University Bloomberg Public School. healthy. Their adaptability to infectious threats other than COVID-19 is also a dream of vaccine researchers.

The mRNA vaccine uses the system our cells use to make proteins. Our cells make proteins based on information in our DNA: each gene encodes a specific protein. Genetic information is essential, but the cell cannot do anything with it until the mRNA molecule converts it into instructions to make a specific protein. This is what mRNA vaccines provide: ready-made mRNA instructions for making specific proteins. As far as these new COVID-19 vaccines are concerned, they are used to produce the "spike" or S protein found on the surface of the SARS-CoV-2 virus.

Vaccines that provide S protein will stimulate the same protective antibody response as exposure to the actual virus. But mRNA vaccines can trigger a particularly strong immune response, Pekosz pointed out, because our own bodies make this protein. "When our cells express foreign proteins, it triggers the recruitment of different types of immune cells and promotes the response," he said. This includes B cells that secrete antibodies and T cells that hunt and kill infected cells.

However, can this protection stand up to new variants of the virus-such as the now widely spread "British variant". It is estimated that the transmission rate of this virus is 40% to 70% higher?

"So far, it appears that mutations in the spike protein in these different variants will not allow the virus to escape the vaccine," said Gigi Gronvall, a senior scholar at the Johns Hopkins University Health Safety Center. But this may change-especially as SARS-CoV-2 continues to spread around the world, each new host creates opportunities for mutations. If these mutations significantly change the structure of the protein, the new variant may avoid antibodies raised by other variant vaccines.

Fortunately, mRNA vaccines are well suited to keep up with sudden changes in the virus landscape. The mRNA itself is manufactured through a standardized process, where the core component is a DNA sequence that encodes a specific viral protein. This means that vaccine manufacturers can update vaccines against new strains by simply adjusting the "formula" to encode new proteins.

"If this virus becomes an endemic virus, new vaccine variants may need to be introduced to match the rooted variants," Gronvall said, noting the seasonal flu vaccine as a parallel line.

As far as Pekosz is concerned, he believes that this method has the potential to defend against highly variable influenza viruses. Efforts have been made to develop mRNA-based "universal" influenza vaccines that can train the immune system against various seasonal or pandemic influenzas.

The additional immune firepower provided by the mRNA vaccine can also produce longer-lasting protection. "We may develop a flu vaccine that theoretically protects us for five years instead of one year," Pecos said. In fact, he believes that the success of the COVID-19 vaccine heralds a bright future against other pathogens.

"If it is external to the virus, then this technology can easily exchange the sequence and generate an immune response [against it]," Pekosz said.

This article originally appeared on the Expert Insights page of the Bloomberg School of Public Health.

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Mark epidemiology, vaccines, covid-19 vaccines, covid-19 variants, mrna