Vaccines generally work by introducing a piece of a virus or bacteria into your body so you can develop long-lasting immunity to the pathogen. While the piece introduced by the vaccine rapidly fades away, your body’s immune system remembers what it saw. When it encounters the virus or bacteria in the real world it mounts a strong immune response preventing or decreasing the severity of infection.
For COVID-19 vaccines, all of the approved vaccines so far used a spike protein. The spike protein is located on the outside of a coronavirus and is how SARS-CoV-2 (the coronavirus) enters human cells. Its location on the outside of the virus makes it so the immune system can recognize it easily.
The spike protein is unique to SARS-CoV-2 – it doesn’t look like other proteins your body makes. So antibodies created against the spike protein won’t harm your body, they will only target coronavirus.
However, the genomic stability of SARS-CoV-2 that scientists had first expected has been disrupted by the emergence of different variants over the course of the COVID-19 pandemic. The N-terminal domain (NTD) of the virus’s spike protein has appeared as a potentially mutable structure—scientists have reported it has deletion-prone regions that may allow the virus to escape antibody neutralization. According to a report posted to medRxiv June 12, the prevalence of these deletions increased during surges of COVID-19 cases worldwide. The study’s authors also report the presence of NTD deletions in SARS-CoV-2 samples from COVID-19 patients who had either been infected before or who were already fully vaccinated.
The team hypothesizes these deletions could assist the virus in evading immunity, potentially playing a role in surges and vaccine breakthrough infections.