Question: Are we heading for a seasonal COVID-19 vaccine like the flu vaccine?
Answer: At least for this fall, it looks like we will have an updated vaccine that is expected to provide some protection against recent variants of SARS-CoV-2, the virus that causes COVID-19.
Last week, Moderna announced that it is developing a “bivalent enhancer” aimed at both the original version of the virus and the highly contagious variant of Omicron, which has led to an increase in COVID-19 cases worldwide in the last few months.
“A bivalent booster can provide comprehensive and long-lasting protection against several different variants, even those for which they were not specifically designed,” Shehzad Iqbal, medical director of Modern Canada, said in an email.
He added that the company is providing clinical data to several government regulators, including Health Canada, in hopes of gaining approval for its new vaccine in the fall.
Another major vaccine manufacturer, Pfizer-BioNTech, is also working on an updated version of its COVID vaccine. Pfizer did not respond to interview requests.
Doctors still advise those who need to receive the booster or fourth injection to receive the scheduled doses and not wait until the fall for the bivalent vaccine to arrive because they would probably experience a decrease in protection before then.
In general, health experts agree that vaccines need to be modified to better adapt to the virus, which has continued to mutate and evolve into new variants.
Vaccines are designed to train the immune system to be alert to a specific pathogen. In the case of SARS-CoV-2, the vaccines target the ear protein, a lumpy lump on the surface of the virus. The immune system generates antibodies that can attach to the ear protein and prevent the virus from invading the cells. If the virus passes through this first line of defense, other specialized immune cells will take action.
However, SARS-CoV-2 has changed so much that antibodies are more difficult to recognize and adhere to ear protein, said Omar Khan, a professor of biomedical engineering and immunology at the University of Toronto.
As a result, people who have received multiple injections of current vaccines may experience innovative infections, although they still retain fairly effective protection against the development of serious illnesses, which can lead to hospitalization and death.
The good news is that both Moderna and Pfizer-BioNTech vaccines are based on easily modifiable messenger RNA, a relatively new approach to creating inoculations.
“You can only synthesize your RNA with basic chemistry,” said Dr. Khan. “The components are mixed and assembled themselves into nice little nanoparticles.”
In comparison, some flu vaccinations are created by the first strains of flu in eggs. These virus particles are then modified for the vaccine, so that the injections trigger an immune response without making people sick.
MRNA vaccines are certainly easier to produce than traditional vaccines. But companies have yet to go through regulatory approval and provide clinical trial data to prove the blows are safe and effective.
“Clinical trials can take months to complete,” said Dr. Khan.
Over time, the COVID-19 vaccine approval process may be streamlined to resemble the regulatory framework used for annual influenza vaccines, which do not require long clinical trials.
“We understand flu vaccines very well. And altering the strains used in them will not change their safety profile,” said Matthew Miller, a professor at McMaster University’s Infectious Diseases Research Institute.
“Obviously, regulators will do their job to make sure the new vaccines are safe.” However, he added that as familiarity with COVID-19 mRNA vaccines increases, clinical trials may no longer be required for the approval of up-to-date vaccinations.
What is still uncertain is how often the vaccines will need to be modified.
The virus has undergone many mutations, in part because it has infected many people. Every time a body invades, there is a risk that it could mutate into a more contagious variant, Dr. Miller said.
As infections decline, “we should expect the rapid rate of onset of variants that we have witnessed over the past two years to begin to decline,” he added.
In turn, a slower rate of viral evolution should mean that our vaccines remain more effective over a longer period of time, said Dr. Khan.
But even if the virus itself doesn’t change much from year to year, there may still be a good reason to offer regular booster injections, said Rob Kozak, a scientist and clinical microbiologist at Sunnybrook Health Sciences Center. of Toronto.
He noted that the number of COVID-19 antibodies circulating in the bloodstream tends to decrease over time after vaccination.
The main task of continuous monitoring of COVID-19 is performed by memory B cells. If they detect the virus, they can be reprogrammed to start producing antibodies. But it may take a while to increase production. Meanwhile, the infected person may experience symptoms of respiratory illness.
A booster shot will increase circulating antibody levels and can help reduce the risk of these infections, Dr. Kozak said.
Another uncertainty is the durability of the protection. We just don’t know how long immunity to COVID-19 lasts, regardless of whether it’s acquired through a vaccine or an actual infection.
Dr. Kozak points out that SARS-CoV-2 is a coronavirus, the same family of pathogens that cause some forms of the common cold.
“If you have a cold, it looks like you’re protected for maybe a year or two and then you can get infected with the same virus again,” he said. “Your immunity tends to wane.”
Researchers may find that COVID-19 immunity decreases in a similar way.
Therefore, for a variety of reasons, public health officials may conclude that COVID-19 vaccine campaigns are needed each year, reflecting the deployment of the annual influenza vaccine.
Fall vaccine administration would increase antibody levels in the community and possibly help mitigate a wave of COVID-19 cases in the winter months when people tend to congregate indoors, a behavior that promotes the spread of respiratory diseases.
Reducing general infections should also reduce the transmission of the virus to vulnerable people who are more likely to develop serious illnesses, such as immunocompromised people and older adults, Dr. Kozak said.
“Promoters can do a wider public health good by providing benefits beyond those who receive vaccinations.”
Paul Taylor is a former patient navigation consultant at Sunnybrook Health Sciences Center and a former health editor at The Globe and Mail.