TORONTO -- Just like influenza vaccines, which are adjusted each year to combat viruses as they change and mutate, COVID-19 vaccines may need similar alterations until infection rates decrease, a recent study suggests.
Influenza viruses are fast-changing, making it difficult for the human body to build an immune response, which is why the flu vaccine is altered and encouraged for everyone each year.
In SARS-CoV-2, the virus that causes COVID-19, mutations allowing it to evade antibodies have already cropped up in the B.1.351 and P.1 variants. Because of this, vaccine producers such as Moderna, Pfizer, AstraZeneca and Johnson & Johnson are already working on boosters for their vaccines to be more effective against variants.
A team of researchers from a German research hospital, Charite-Universitatsmedizin Berlin, looked at four common cold coronaviruses that infect humans by the same spike protein mechanism that SARS-CoV-2 uses.
The research, published in the journal Virus Evolution on March 20, focused attention on two of the longest known coronaviruses and studied their evolution over the course of 40 years, according to a press release. Researchers built a phylogenetic tree - a tree-shaped diagram that shows the evolutionary process of various specimens and species - showing the evolutionary progress of the coronaviruses.
They then compared it to the phylogenetic tree of H3N2, a strain of the influenza virus that is known for its ability to evade the immune response.
Researchers found a similarity in their comparisons: they all had a ladder shape.
"An asymmetrical tree of this kind likely results from the repeated replacement of one circulating virus variant by another which carried a fitness advantage," the study's first author, Dr. Wendy K. Jo from Charite's Institute of Virology, said in the press release.
“This is evidence of 'antigenic drift', a continuous process involving changes to surface structures which enable viruses to evade the human immune response. It means that these endemic coronaviruses also evade the immune system, just like the influenza virus. However, one also has to look at the speed with which this evolutionary adaptation happens," she added.
Researchers were able to determine the speed at which the viruses evolved, with influenza viruses mutating four times faster than the coronaviruses, the release said.
“As far as SARS-CoV-2 is concerned, this is good news," Dr. Christian Drosten, Director of the Institute of Virology and a researcher at the German Center for Infection Research, said in the release.
However, SARS-CoV-2 is mutating at a faster rate than the coronaviruses in the study, but researchers believe this is due to the rate of infections across the globe.
“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,” lead study author Dr. Jan Felix Drexler, said in the release.
Once the COVID-19 pandemic has stabilized and numbers being to drop off in earnest, vaccine updates will become less common, but until then they will need to be altered for variants, the release said.
“We expect therefore that COVID-19 vaccines will need to be monitored regularly throughout the pandemic and updated where necessary. Once the situation has stabilized, vaccines are likely to remain effective for longer,” said Felix Drexler.
