Question

Some viral diseases (e.g. influenza and dengue fever) are thought to exhibit original antigenic sin. The immune system remembers viruses that it has been previously exposed to, allowing the body to mount an effective defense if the same virus is seen again. However, in some cases, this immunological memory can be overly specific. When the body is exposed to a new variant of a familiar virus, it produces antibodies against the old variant rather than the new variant. If these antibodies are less effective against the new variant, the infection can be more severe than it would have been in a person with a naive immune system.

Is there reason to believe that the same phenomenon could occur for Sars-CoV-2 and its variants? In particular, could people who were infected by or vaccinated against the original strain be more vulnerable to Omicron or other future variants?

Answer 1

Original antigenic sin could make previous exposures to earlier strains or vaccinations less protective against new virus variants like SARS-CoV-2's Omicron. The immune system's memory might be less effective due to the virus's rapid antigenic variation, a challenge that also necessitates updating vaccines like the annual flu shots.

Step-by-step explanation:

The phenomenon known as original antigenic sin refers to the immune system's preference for producing antibodies against a previously encountered variant of a virus, rather than a new variant. This can make subsequent infections with new variants more severe. In the context of SARS-CoV-2, which has produced multiple variants such as Omicron, there is concern that this phenomenon could result in people who were infected with or vaccinated against the original strain being less effectively protected against new variants.

Vaccinations work by introducing noninfectious antigens to elicit an immune response that results in immune memory. However, viruses like HIV and Influenza, and potentially SARS-CoV-2, undergo rapid antigenic variation. As a result, the antibodies generated may not recognize and effectively combat new strains, necessitating the development of new vaccines and potentially additional booster vaccinations to deal with newly emerging strains.

The term 'antigenic drift' explains why flu vaccines must be updated annually. It suggests that similar challenges may be faced with SARS-CoV-2 variants. This illustrates the dynamic and adaptive challenge that viruses pose to our immune systems and the ongoing need for updated vaccinations to maintain effective immune protection.