Last April, this column explained how the treatment of many diseases, including COVID-19, has been transformed by the use of vaccines created with mRNA. Vaccines stimulate the body’s immune response against a germ without exposing the individual to the disease-causing germ itself. Proteins from the surface of a germ are used in vaccines to stimulate an immune response. The basic function of mRNA is to read a DNA gene sequence in order to produce a specific protein.

The coronavirus mRNA vaccines contain mRNA molecules with the gene sequence that code for the coronavirus spike protein. This protein is located on the outside of a coronavirus, and it enables the entry of the virus into human cells. Its location on the outside of the virus allows the immune system to detect it. Once inside the body, the vaccine’s mRNA sequence is used to produce the coronavirus spike protein. This protein then initiates a response by the immune system to provide immunity to the coronavirus. New mRNA vaccines can be produced quickly by inserting additional genetic codes into the vaccine.

The coronavirus has evolved rapidly since it was first identified in January 2020 as the cause of COVID-19. There are now many variants around the world that have different transmissibility, severity, and immune evasion. The coronavirus has a very high mutation rate. Mutations are random errors during virus replication, and most of them are harmful to the virus and disappear. However, some mutations are advantageous to the virus and therefore increase in frequency. For example, the D614G mutation had a 20% transmissibility advantage when it emerged in 2020, and it quickly climbed to high frequency around the world.

Some COVID-19 variants carry many mutations. For example, the omicron variant carries over 50 mutations. Most of these mutations occurred in the spike protein, which made it harder for the existing vaccines to detect and neutralize the virus. The omicron variant was first detected in November 2021, and it quickly spread to become the predominant variant around the world. Omicron is more infectious than previous variants, but there is no evidence that it causes greater sickness.

In September, approval was given to a new batch of COVID-19 vaccines that are a closer match to the coronavirus variants that are currently in circulation. These new vaccines are called bivalent because they protect both against the original strain of coronavirus and against more recent variants. This helps the COVID-19 vaccines keep pace with the ongoing evolution of the virus.

The Nobel Prize Committee stated that they hoped that the award would encourage hesitant people to take the vaccine because it is effective and safe. A total of over one million people have died in the U.S. with COVID-19; most of these people were unvaccinated. The accompanying figure shows the weekly age-adjusted deaths per 100,000 people for unvaccinated people and people vaccinated with the original vaccine. Vaccination with the booster using the bivalent vaccine has provided even greater protection. Death rates among persons vaccinated with the bivalent vaccine were 93% lower than death rates of unvaccinated persons in late 2022. The evidence is overwhelming that the mRNA vaccine provides effective protection again COVID-19.