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Health – Flu vaccines need to be updated every year to protect against new influenza viruses. Will this also be necessary for COVID-19 vaccines? In order to be able to estimate this, a research team from Charité – Universitätsmedizin Berlin compared the evolution of common cold coronaviruses with that of flu viruses. The researchers’ prognosis: regular vaccine updates will be necessary during the pandemic, but a longer shelf life of the vaccines can be expected after a few years. The study was published in the specialist magazine Virus Evolution *.
Influenza viruses are masters at evading human immune reactions: They change so quickly that the antibodies that the immune system produced after an earlier infection or vaccination can no longer recognize them well. This means that the vaccine has to be laboriously adapted in practically every flu season. SARS-CoV-2 has also produced various mutants, some of which, such as the so-called South African variant, partially undermine the immune reaction. The first vaccine manufacturers are therefore already developing new versions of their vaccines. What does that mean for the future? Will COVID-19 vaccines like the flu vaccines need to be updated regularly?
In order to be able to assess whether SARS-CoV-2 will show an equally pronounced “flight” from the immune system in the long term as influenza viruses, virologists at the Charité have examined the genetic development of cold coronaviruses. Four such comparatively harmless corona viruses are known, which are around 10 percent of colds worldwide cause and have been circulating in humans for much longer than SARS-CoV-2. They also enter human cells via the so-called spike protein, which forms the eponymous “crown” on the virus surface and against which all previous COVIDs -19 vaccines are targeted.
For the study, the research team tracked how the spike gene of the two longest known coronaviruses 229E and OC43 has changed over the past 40 years. To do this, the scientists compared the sequences from samples of different ages that had been stored in a gene database and, based on the mutations that had developed over time, developed a family tree for both coronaviruses. For comparison, the researchers looked at the influenza strain H3N2, which evades the human immune reaction particularly efficiently.
The calculated family trees of both the coronavirus and the influenza virus had one thing in common: They showed a pronounced staircase shape. “Such an asymmetrical family tree means that one circulating virus line is regularly replaced by another because it has a survival advantage,” explains Dr. Wendy K. Jó, first author of the study from the Institute of Virology at the Charité So-called antigen drift, i.e. a continuous change in the surface structures through which viruses evade the human immune reaction. The domestic coronaviruses therefore escape the immune system just like the flu virus. However, you also have to look at the speed with which this evolution takes place. “
To do this, the research team determined the evolution rates of the three viruses. While 25 mutations per 10,000 genetic components accumulated in the influenza sequence per year, there were only around six mutations in the coronaviruses. This means that the common coronaviruses changed four times more slowly than the flu virus. “This is good news with a view to SARS-CoV-2,” summarizes Prof. Dr. Christian Drosten, Director of the Institute for Virology and scientist at the German Center for Infection Research (DZIF).
Because the rate of evolution of SARS-CoV-2 is currently estimated at around ten mutations per 10,000 genetic components per year, significantly higher than that of the common coronaviruses. “This rapid genetic change in SARS-CoV-2 is reflected in the emergence of many different virus variants worldwide,” explains Prof. Dr. Jan Felix Drexler, head of the study from the Institute of Virology and DZIF researcher mainly in the high infection rate during the pandemic: Where there are many infections, a virus can also develop faster. Based on the evolution rates of the domestic cold corona viruses, we assume that SARS-CoV-2 will also change more slowly as soon as the infection occurs dies down – after a large part of the global population has built up immune protection either through the disease itself or through a vaccination. We therefore assume that the COVID-19 vaccinations will have to be checked regularly during the pandemic and, if necessary, adjusted The situation has stabilized, the vaccinations will probably be usable for longer. “
A press release from the Charité Universitätsmedizin Berlin