With the vaccination campaigns against COVID-19 active around the world, one of the great unknowns is, in addition to the duration of said immunity, whether it will be necessary to modify the vaccines each year to prevent the new variants of SARS-CoV- 2 bypass our immune system. To try to answer this question, a team of German researchers has compared the evolution of coronaviruses that cause the common cold with that of influenza viruses.
The results, published in the journal Virus Evolution , indicate that as the pandemic continues, vaccines should undergo regular updates. However, within a few years of the post-pandemic period, it is likely that vaccines can become effective for longer.
The four common cold coronaviruses
The four coronaviruses that we know to cause what we call the ‘common cold’ are known to be responsible for approximately 10% of the world’s mild colds, and have been in circulation among humans considerably longer than SARS-CoV- two. Its mechanism of entry into cells is very similar, through the now famous protein S, which is in turn the target of all the COVID vaccines currently on the market.
The researchers tracked changes in the gene that codes for the protein in two of the best-known coronaviruses over the past 40 years and compared them to the H3N2 phylogenetic tree, a flu subtype that is particularly adept at evading the virus. human immune response. The results revealed that, while the common cold coronaviruses are also capable of evading the human immune system, their evolutionary adaptation takes place at a much slower rate than that of the flu.
Specifically, the rate of change for coronaviruses was four times slower than that of the flu virus. “As far as SARS-CoV-2 is concerned, this is good news,” sums up Christian Drosten, director of the Institute for Virology and researcher at the German Center for Infection Research (DZIF). Currently it is estimated that SARS-CoV-2 changes at a rate of approximately 10 mutations per 10,000 nucleotides per year, which means that the rate at which it evolves is substantially greater than that of the common cold coronaviruses.
“This rapid genetic change in SARS-CoV-2 is reflected in the appearance of numerous virus variants around the world,” explains study leader Jan Felix Drexler, a researcher at the Institute of Virology and DZIF. “However, this is likely due to the high infection rates seen during the pandemic. When infection numbers are this high, a virus can evolve more rapidly. Based on the evolution rates seen in endemic coronaviruses of the common cold, we hope that SARS-CoV-2 begins to change more slowly once infections begin to disappear, that is, once a large proportion of the world’s population has developed immunity, either as a result of infection or through vaccination ” .
Referencia: Jo WK et al. The evolutionary dynamics of endemic human coronaviruses. Vir Evol 2021. doi: 10.1093/ve/veab020
