5 Summary

Since it first appeared, the SARS-CoV2 virus has evolved and new pandemic strains have emerged. Many 1000s of variants have been identified by genome sequencing, but only a few of them are designated as variants of interest (VOI) , and fewer still variants of concern (VOC), that spread widely or produce particularly serious disease. New pandemic strains can displace earlier strains if they can replicate more efficiently, evade immune responses, or spread in the community more effectively.

Genetic variation can occur throughout the genome, but it particularly affects the spike protein, because changes in the spike protein allow the virus to attach more effectively to target cells and/or evade antibodies.

Using genomic sequences, it is possible to reconstruct lineages for the different VOCs. The lineages show how the alpha, delta and omicron variants, which have high R₀ values, have also diversified considerably. As new VOCs have emerged, they spread across the world from their point of origin, eventually replacing previous VOCs, which have gone extinct in the general population.

New VOCs have partially evaded antibody-mediated immunity produced by previous strains or by the earlier vaccines. This means that reinfection with new strains does occur. However the residual antibody and T cell immunity still provides some protection, so that any disease from infection, is much less serious in a person who has been previously infected or vaccinated. Booster doses of vaccine can help maintain this residual immunity, and vaccines are being reformulated to include antigens from later variants.

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DAVID MALE:

We hope you have enjoyed this course on the Immunology and epidemiology of COVID-19. Much of what you have learnt applies more widely to other respiratory virus infections such as influenza. The scientific community has learnt an enormous amount from the COVID-19 pandemic, partly because it has been the first time that rapid genomic analysis was widely available to study viral variants and their global spread. In addition the technology for producing vaccines took a major step forward with the development of the mRNA and vector vaccines.

We also hope that using the on-line ELISA laboratory has given you some insight into what occurs in laboratories that are developing vaccines or trying to estimate where a virus has spread in a community. The ELISA technique is widely used in immunology and related disciplines for measuring antibodies and other proteins in biological fluids; it is not just for detecting serum antibodies against SARS-CoV2. So the scientific and technical methods that you have learnt on this course are more generally applicable.

If you want to take your studies further or achieve a qualification in this area, The Open University has a Health Science degree programme which includes modules that cover infection, immunity and public health and many other areas of the Health sciences.

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Now you’ve come to the end of the course, we would appreciate a few minutes of your time to complete this short end-of-course survey [Tip: hold Ctrl and click a link to open it in a new tab. (Hide tip)] (you may have already completed this survey at the end of Week 4).