Influenza viruses are a moving target, forcing drug developers to modify their products annually based on the strains most likely to dominate a given season.
SARS-CoV-2 could follow a similar trajectory in the first few years of the pandemic, according to a study published in Virus Evolution. SARS-CoV-2 is likely to continue to accumulate changes in the receptor binding domain of the spike protein, prompting updates to vaccines over time.
But assuming COVID-19 infection rates are relatively low over the next several years, vaccines are likely to need less-frequent updating, they concluded.
The researchers from the Charité–Universitätsmedizin Berlin in Germany arrived at their conclusions by studying how two other human coronaviruses have evolved over the past four decades. The coronaviruses they studied are known as 229E and OC43.
The coronaviruses 229E and OC43 have steadily evolved to evade the human immune system, but at a much slower rate than influenza viruses. That is, while an influenza virus accumulates roughly 25 mutations per 10,000 nucleotides, coronaviruses accumulate about six such mutations.
In recent months, SARS-CoV-2 has evolved rapidly for a coronavirus. One factor enabling the current phase of relatively rapid evolution of the virus is the high number of cases in late 2020 and early 2021.
But growing level of immunity across the human population could limit the opportunities for the virus to evolve. “Based on the rates of evolution seen in the endemic common cold coronaviruses, we expect that SARS-CoV-2 will start to change more slowly once infections start to die down — meaning once a large proportion of the global population has developed immunity either as a result of infection or through vaccination,” said study lead Dr. Jan Felix Drexler, a researcher at both the Institute of Virology and the German Institute for Infection Research in a statement.