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A P R I L 2021 ME S S E NG E R
VACCINE PRODUCTS What vaccines are available and how do they work? The first COVID-19 vaccines available in Alberta are the Pfizer and Moderna vaccines. Both are mRNA vaccines. An mRNA vaccine is a new type of vaccine that prepares the body to defend and protect itself against infectious diseases – in this case, COVID-19. The mRNA vaccine teaches your body’s cells to make a viral protein that triggers the immune response. When a person is given the vaccine, their body’s cells will read the instructions from the mRNA and produce the harmless “spike protein” which is the same protein that is normally found on the surface of the COVID-19 virus, but not found in our bodies. The person’s immune system will then treat this spike protein as foreign and produce defenses to fight against it. These defenses are then ready to protect the person against the real COVID-19 virus. Why does the mRNA vaccine need to be frozen? The mRNA vaccine is stored in frozen or ultra-frozen temperatures because mRNA is more likely to break down above freezing temperatures. To ensure the vaccine will work the best when it is administered, the vaccine is stored frozen before ready to use. The manufacturers continue to study the stability of the vaccine in various storage conditions and the temperature guidelines for storage may change in the future. VACCINE EFFECTIVENESS How effective is the vaccine? The initial Pfizer and Moderna COVID-19 vaccines available for use in Canada have been demonstrated to be over 90% effective in preventing COVID-19 disease in clinical trials. What is the difference between vaccine efficacy and effectiveness? ‘Vaccine efficacy’ is the term used to describe the percentage reduction of disease in an immunized group of people compared to an unimmunized group in clinical trials where the study conditions are controlled. It does not describe whether an immunized person can still transmit the virus. ‘Vaccine effectiveness’ is the term used to describe how the vaccine works in the real world where conditions cannot be controlled, such as previous exposure to the virus, the immune status of the individual, and if people receive both doses that are required. Vaccine effectiveness will continue to be evaluated as the COVID-19 immunization program is rolled out. The vaccines are reported to have different efficacy rates against COVID-19. Is a vaccine with a higher reported vaccine efficacy better than a vaccine with a lower efficacy? It may seem that 90% is better than 80% when looking at vaccine efficacy, however, with vaccines it is not that simple. Efficacy does not mean effectiveness. Efficacy refers to the difference in infection rates between a group that got a vaccine, and a group that did not. If there’s no difference between the two groups, efficacy is zero. Differences in efficacy numbers may be because the vaccines were tested in different locations, at different phases of the pandemic, against different strains and over different schedules (e.g., one vs. two doses over different timeframes). What is important to know is the COVID-19 vaccines are demonstrating a reduction in hospitalizations, deaths and severe disease. Health Canada would not approve a vaccine if they determined it to be insufficient to protect against disease. Will the vaccine work against the COVID-19 variant strains? Mutations in the COVID-19 virus over time are expected, and can cause variant strains of COVID-19 to emerge. At this time, there are several variant strains circulating around the world, and vaccine manufacturers are conducting studies to determine whether current vaccines work against these variants. We are watching this information closely.
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