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A26-27 I sCanada' of business risky the nside d teels old ,seas oughr ,money big ships: ead Brokenvessels WEATHER HIGH 27 C | THUNDERSTORMS |MAP A28 SATURDAY, JUNE 26, 2021 The MV Miner ran aground in Nova Scotia in 2011, crashing onto the shores of Scatarie Island, a pristine environmental area protected by the province. DEPARTMENT OF NATURAL RESOURCES AND NOVA SCOTIA ENVIRONMENT STAR INVESTIGATION Pfizer and BioNTech have an- nounced they will be seeking ap- proval for a third dose of CO- VID-19 vaccine to act as a booster in the coming months, stirring up mixed feelings among scientists and experts who are unsure if an additional dose is necessary. On July 8, the companies re- leased a joint statement saying that initial data from their boost- er trial demonstrates that a third dose given six months after the second significantly improves immune response against the Be- ta variant and they believe a third dose "has the potential to pre- serve the highest levels of protec- tive efficacy against all currently known variants including Delta ..." When speaking about the pos- sibility of rolling out a COVID-19 booster to all Canadians, Tania Watts, professor of immunology at University of Toronto, said it is still too early to tell whether it will be needed. At this point, she said, data shows "very little drop off in anti- body or T cell responses" in peo- ple who have been fully vaccinat- ed. "Some vaccines give lifelong immunity (and) some need peri- odic boosters and this is a new vaccine so we have to just watch over time," she added. "If we start to get more breakthrough infec- tions in the vaccinated, or if stud- ies that are ongoing to measure antibody levels find they start to drop off, then we may need to have a population-wide booster, but I don't think we need it now." Watts explained there are two potential scenarios that would in- dicate a booster shot is warrant- ed: if data starts to show immuni- ty dropping off over the next few months, or if a variant emerges that escapes the vaccine. Reggie Lo, professor emeritus in the department of molecular and cellular biology at the Uni- versity of Guelph, said the chanc- es of a new variant emerging that is so different from the original strain of SARS-CoV-2 that it will render the country's current vac- cines ineffective is "quite unlike- ly." This is because when random mutations occur, there are limit- ed amino acid positions that can have amino acid substitutions without affecting the proper fold- ing and function of the protein, Lo explained. "There is a finite number of tolerable changes to the viral spike protein without destroying its function," he added. "Hence, it is unlikely that there will be a variant with a spike protein so vastly different from the initial SARS-CoV-2 that the current vac- cine will become completely inef- fective." HOW DOES A BOOSTER WORK? The first time a person re- ceives a vaccine dose, their im- mune system recognizes that something is new and makes anti- bodies and generates T cells that can recognize infected cells. That immune response takes a week or two to develop and then slowly decreases over time but leaves behind memory cells -- called lymphocytes -- that are trained to see that new infection and respond rapidly, Watts ex- plained. Every time that person re- ceives a subsequent dose, "the cells that make the antibodies ac- tually undergo changes that make stronger antibodies," she added. "So the boost is very good but the question becomes do we need a third one? Evidence is not yet there." Watts said there are a number of current studies measuring the level of antibodies required for protection and once that is deter- mined, scientists can start to monitor the level of antibodies people have. Then a population- wide decision will likely be made as to whether boosting will be re- quired. Lo said he thinks an eventual booster will be most beneficial for those who are vulnerable, as well as health-care workers and oth- ers who are in contact with them. "The antibody levels are still giving us protection against even the variants, but of course as time goes on, the elderly and those who might not have a strong immune response will have a declined pro- tection," he noted. WILL WE NEED A THIRD DOSE COVID-19 BOOSTER? EXPERTS WEIGH IN The Haldimand Norfolk Health Unit is continuing to urge students aged 12 to 17 to get their coronavirus vaccinations in preparation for a return to the classroom in the fall. Metroland file photo VERONICA APPIA vappia@toronto.com NEWS 'EVIDENCE IS NOT THERE YET': IMMUNOLOGIST