Answer: At least for this fall, it looks like we will have an up-to-date 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 was developing a “bivalent amplifier” targeting both the initial version of the virus and the highly contagious Omicron variant, which has caused an increase in COVID-19 cases worldwide in recent months. “A dual amplifier can provide broad, durable protection against many different variants, even those not specifically designed to target,” Shehzad Iqbal, Moderna Canada’s medical director, said in an e-mail. He added that the company is providing clinical data to various government regulators, including Health Canada, in hopes of getting approval for its new vaccine by the fall. Another major vaccine manufacturer, Pfizer-BioNTech, is also working on an updated version of its COVID vaccine. Pfizer did not respond to a request for an interview. Doctors continue to advise those who need to have their booster or fourth vaccination to take their doses as scheduled and not wait for the bivalent vaccine to arrive in the fall, as they will likely experience reduced protection before then. Health experts generally agree that there is a need to modify vaccines to better match the virus, which has continued to mutate and evolve into new variants. Vaccines are designed to train the immune system to be on the lookout for a specific pathogen. In the case of SARS-CoV-2, the vaccines target the spike protein, a protrusion on the surface of the virus. The immune system produces antibodies that can attach to the spike protein and prevent the virus from invading the cells. If the virus crosses this first line of defense, other specialized immune cells will jump into action. However, SARS-CoV-2 has changed so much that antibodies are difficult to recognize and attach to the pin protein, said Omar Khan, a professor of biomedical engineering and immunology at the University of Toronto. As a result, people who have received multiple shots with the current vaccine may develop unprecedented infections, although they still maintain fairly effective protection against the development of severe disease, which can lead to hospitalization and death. The good news is that vaccines made by both Moderna and Pfizer-BioNTech are based on easily modifiable messenger RNA – a relatively new approach to vaccine development. “You can only synthesize your RNA with basic chemistry,” Dr. Khan explained. “You mix the ingredients together and they assemble themselves into nice little nanoparticles.” By comparison, some flu vaccines are created with the first development of influenza strains in eggs. These virus particles are then modified for the vaccine so that the vaccines activate an immune response without actually making humans sick. MRNA vaccines are definitely easier to produce than traditional vaccines. However, companies must go through regulatory approval and provide clinical trial data to prove that the notches are safe and effective. “Clinical trials can take months to complete,” he said. 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 major clinical pathways. “We understand the flu vaccine very well. “And changing the strains used in them is not going to change their safety profile,” said Matthew Miller, a professor at the Infectious Diseases Research Institute at McMaster University. “Obviously, regulators will do their job to make sure the new vaccines are safe.” However, he added, as familiarity with COVID-19 mRNA vaccines increases, clinical trials may no longer be required to approve updated shots. What remains uncertain is how often vaccines should be modified. The virus has undergone many mutations, in part because it has infected so many people. “Every time it invades a body, there is a risk that it will mutate into a more contagious variant,” Dr. Miller said. “As infections decrease,” we should expect the rapid rate of variation we have seen over the past two years to begin to slow, “he added. “In turn, a slower rate of virus progression should mean that our vaccines remain more effective for a longer period of time,” said Dr. Khan. But even if the virus itself does not change much from year to year, there may be a good reason to get regular booster vaccines, said Rob Kozak, a scientist and clinical microbiologist at the Sunnybrook Health Sciences Center in 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 some time to increase their production. In the meantime, the infected person may show symptoms of respiratory disease. A booster vaccine will increase circulating antibody levels and may help reduce the risk of such infections, Dr. Kozak said. Another uncertainty is the durability of the protection. We just do not know how long COVID-19’s immunity lasts – whether it is acquired through a vaccine or a real infection. Dr. Kozak points out that SARS-CoV-2 is a coronavirus – the same family of pathogens that cause certain forms of the common cold. “If you catch a cold, you seem to be protected for maybe a year or two and then you can get the same virus again,” he said. “Your immunity tends to weaken.” Researchers may find that immunity to COVID-19 decreases in a similar way. Thus, for a variety of reasons, public health officials may conclude that COVID-19 vaccine campaigns are required each year – reflecting the release of the annual flu vaccine. Vaccination in the fall would increase antibody levels in the community and possibly help alleviate a wave of COVID-19 cases during the winter months, when people tend to concentrate indoors – a behavior that favors the spread of respiratory illness. Reducing overall infections should also reduce the transmission of the virus to vulnerable people who are more likely to develop serious illnesses, such as the immunocompromised and the elderly, Dr Kozak said. “Amplifiers can deliver a wider public health benefit by providing a benefit beyond those receiving the downloads.” Paul Taylor is a former patient navigation consultant at the Sunnybrook Health Sciences Center and a former health editor for The Globe and Mail.
