How long will the vaccines stay effective?
How long the protection really lasts after a vaccination against COVID-19 is also influenced by how many new variants of the virus are created, because in the worst case these can evade the immune reaction triggered. It is already evident that regular adjustments to the COVID-19 vaccines will probably be necessary. So do we need new vaccines next year?
In a current study, researchers at Charité – Universitätsmedizin Berlin compared the evolution of common coronaviruses and influenza viruses, from which statements about the duration of vaccination protection can be derived. Because flu vaccines have to be adjusted annually in view of the continuous changes in the viruses. The researchers are now expecting the same for the COVID-19 vaccines, albeit with the hope that after a few years the periods between vaccinations can be extended. The study was published in the specialist journal Virus Evolution.
Flu vaccines need to be adjusted annually
“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,” explain the Charité researchers. An extensive adjustment of the vaccine is necessary in practically every flu season.
Mutants can undermine immune reactions
In the case of SARS-CoV-2, the first mutants such as the so-called South African variant can also partially undermine the immune reaction after a vaccination. “The first vaccine manufacturers are therefore already developing new versions of their vaccines,” reports the Charité. In the current study, the researchers therefore tried to find out whether SARS-CoV-2 will show an equally pronounced “flight” from the immune system in the long term as influenza viruses.
Comparison of evolution
To do this, they compared the evolution of two known, rather harmless coronavirus strains (229E and OC43), which have been circulating in humans for much longer than SARS-CoV-2, with the evolution of viruses of the influenza strain H3N2. For the study, the research team tracked how the spike gene of the two longest known coronaviruses has changed over the past 40 years and, based on the mutations that have developed over time, developed a family tree for both coronaviruses.
Stair-shaped family trees
They compared this family tree with that of the influenza strain H3N2, which evades the human immune reaction particularly efficiently. Both family trees 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 the study’s lead author, Dr. Wendy K. Jó from the Institute for Virology at the Charité – Universitätsmedizin Berlin.
Antigen drift in influenza and coronaviruses
According to the virologist, this is “an indication of a so-called antigen drift, i.e. a continuous change in the surface structures through which viruses evade the human immune reaction.” Both the coronaviruses and the flu viruses therefore repeatedly escape the immune system through changes. “However, you also have to look at the speed with which this evolution is taking place,” emphasizes the expert.
Flu viruses change faster
To do this, the researchers determined the evolution rates of the three viruses. It became clear that 25 mutations per 10,000 genetic components accumulated in the influenza sequence per year, while there were only around six mutations in the coronaviruses. Accordingly, the common coronaviruses changed four times more slowly than the flu virus, which is “good news with a view to SARS-CoV-2,” said Professor Dr. Christian Drosten, Director of the Institute for Virology at Charité – Universitätsmedizin Berlin.
More mutations when there is a high infection rate
The rate of evolution of SARS-CoV-2 is currently, with an estimated ten mutations per 10,000 genetic components per year, still significantly higher than that of the coronaviruses examined, which is also reflected in the occurrence of many different virus variants worldwide, according to the head of the study, Professor Dr. Jan Felix Drexler from the Institute for Virology at Charité – Universitätsmedizin Berlin. However, the reason for this lies mainly in the high level of infection during the pandemic
“Where there are many infections, a virus can develop more quickly. Based on the evolution rates of domestic cold coronaviruses, we assume that SARS-CoV-2 will also change more slowly as soon as the infection process subsides – i.e. after a large part of the global population has built up immune protection either through the disease itself or through a vaccination ” , emphasizes Professor Drexler.
Vaccines can be used longer in the future
The researchers come to the conclusion that the COVID-19 vaccinations must be checked regularly during the pandemic and adjusted if necessary. As soon as the situation has stabilized, the vaccinations are expected to be usable for a longer period. “Regular vaccine updates will be necessary during the pandemic, but after a few years a longer shelf life of the vaccines can be expected,” the Charité summarizes the study results. (fp)
Author and source information
This text complies with the requirements of specialist medical literature, medical guidelines and current studies and has been checked by medical professionals.
- Charité – Universitätsmedizin Berlin: Do COVID-19 vaccines have to be regularly readjusted in the future? (published March 25, 2021), charite.de
- Wendy K. Jo, Christian Drosten, Jan Felix Drexler: The evolutionary dynamics of endemic human coronaviruses; in: Virus Evolution (veröffentlicht 20.03.2021), academic.oup.com
This article is for general guidance only and is not intended to be used for self-diagnosis or self-treatment. He can not substitute a visit at the doctor.