question: Are we targeting 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 the latest variants of SARS-CoV-2, the virus that causes COVID-19.
Last week, Moderna announced that it was developing a “bivalent booster” targeting both the original version of the virus and the highly contagious version of Omicron, which has sparked a surge in COVID-19 worldwide in recent months.
“The bivalent booster can provide broad and lasting protection against several different options, even those not specifically designed for targeting,” said Shehzad Iqbal, medical director of Moderna Canada, in an email.
He added that the company is providing clinical data to various government regulators, including Health Canada, in hopes of receiving approval for its new vaccine by the fall.
Another major vaccine manufacturer, Pfizer-BioNTech, is also working on an updated version of its COVID photo. Pfizer did not respond to interview requests.
Doctors are still advising those who need to receive a booster or a fourth injection, to receive their scheduled doses and not to wait until the autumn for the arrival of the bivalent vaccine, because they are likely to experience declining protection before that.
Health experts generally agree that vaccines need to be modified to better respond to the virus, which continues 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 thorn protein, a protrusion on the surface of the virus. The immune system generates antibodies that can bind to thorn protein and prevent the virus from invading cells. If the virus passes through this first line of defense, other specialized immune cells will begin to function.
However, SARS-CoV-2 has changed so much that antibodies have a harder time recognizing and adhering to thorn 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 develop sudden infections, although they still retain fairly effective protection against the development of a serious illness that can lead to hospitalization and death.
The good news is that vaccines made by both Moderna and Pfizer-BioNTech are based on easily modified messenger RNA – a relatively new approach to creating inoculations.
“You can only synthesize your RNA with basic chemistry,” Dr. Hahn explained. “You mix the components together and they come together into nice little nanoparticles.
By comparison, some flu vaccines are made from the first strains of flu in eggs. These virus particles are then modified for the vaccine so that the injections elicit an immune response without actually making people ill.
RNA vaccines are certainly easier to produce than traditional vaccines. But companies still need to go through regulatory approval and provide clinical trial data to prove that the strikes are safe and effective.
“Clinical trials can take months to complete,” Dr. Hahn said.
Over time, the COVID-19 vaccine approval process may be streamlined to resemble the regulatory framework used for annual influenza vaccines that do not require long clinical pathways.
“We understand flu vaccines very well. And changing the strains used in them will not change their safety profile, “said Matthew Miller, a professor at McMaster University’s Institute for Infectious Diseases Research.
“Obviously, regulators will do their job to make sure the new vaccines are safe.” But, he added, as awareness of COVID-19’s mRNA vaccines increased, clinical trials may no longer be required to approve updated photos.
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 so many people. Every time it invades the body, there is a risk of mutating into a more contagious variant, Dr. Miller said.
As infections decline, “we should expect the rapid rate of variation we have seen in the last few years to begin to slow,” he added.
For its part, a slower rate of viral evolution should mean that our vaccines remain more effective for longer periods of time, Dr. Hahn said.
But even if the virus itself doesn’t change much from year to year, there may still be a good reason to make regular booster vaccines, said Rob Kozak, a scientist and clinical microbiologist at the Sunnybrook Center for Health Sciences in Toronto.
He noted that the number of COVID-19 antibodies circulating in the bloodstream tended to decrease over time after vaccination.
The main task of current 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 some time to increase production. In the meantime, the infected person may experience symptoms of respiratory disease.
The booster injection will increase circulating antibody levels and may help reduce the risk of such infections, Dr Kozak said.
Another uncertainty is the longevity of protection. We simply do not know how long immunity against COVID-19 lasts – whether it is 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 get a cold, it looks like you’ve been protected for maybe a year or two and then you can get the same virus again,” he said. “Your immunity tends to decrease.”
Researchers may find that immunity to COVID-19 decreases in a similar way.
So, for various reasons, public health officials may conclude that COVID-19 vaccine campaigns are needed every year – reflecting the spread of the annual flu vaccine.
Vaccines in the fall will increase antibody levels in the community and are likely to help blunt the wave of COVID-19 cases during the winter months, when people tend to gather indoors, a behavior that is conducive to the spread of respiratory diseases.
Reducing common infections should also reduce the transmission of the virus to vulnerable people who are more likely to develop severe disease, such as immunocompromised and elderly people, Dr. Kozak said.
“Boosters can bring greater benefits to public health by providing benefits beyond those who receive vaccines.”
Paul Taylor is a former patient navigation advisor at the Sunnybrook Health Science Center and a former health editor at The Globe and Mail.
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