Shradha Madur, PharmD Candidate, Markland Wood Pharmacy.
Scientists are actively working to develop potential antivirals and vaccines for COVID-19 prevention. This pandemic has infected over 3.8 million people globally. However, it is reassuring that vaccine development is underway in many countries to help minimize further spread of the virus.
Vaccines work by imitating an infection and causing our immune system to develop antibodies and memory cells. These antibodies and memory cells then help the immune system learn how to protect itself against a disease. In general, the more similar a vaccine is to the disease-causing germ, the better the immune system response will be. Vaccines can help achieve a type of protection called “herd immunity”. Herd immunity occurs when a sufficient number of people in a population are immune to a disease (through a vaccine for example) so that the infection does not spread within that group.
There are 5 main types of vaccines:
- Live-attenuated vaccines have a weakened live version of the germ. Since it is weakened, it does not cause the disease when injected and provides a strong and long-lasting immune response. Examples are MMR and chickenpox vaccines.
- Inactivated vaccines contain a killed version of the germ. Thus, the immune response is not as strong as a live-attenuated version, and multiple doses are required to develop and/or maintain immunity. Examples are Polio, Hepatitis A and Flu vaccines.
- Subunit, conjugate, recombinant and polysaccharide vaccines contain a specific piece of the germ, such as a protein or sugar capsule. Because the immune response in these vaccines is to a specific target, the immune response is very strong. A limitation of these vaccines though, is that booster shots may be required to ensure long-lasting protection. Examples are Hepatitis B and Pneumococcal vaccines.
- Toxoid vaccines contain a toxin protein from the germ that is responsible for causing the disease. Thus, the immune response is towards this specific toxin and not the germ. This type of vaccine often requires booster shots for ongoing protection against the disease. Examples are Diptheria and Tetanus vaccines.
- DNA and mRNA vaccines are made using the genetic code (DNA or mRNA) of the germ. There are currently no approved DNA or mRNA vaccines. However, several vaccines underway for COVID-19 are using this technology, as discussed below. Researchers are specifically using an inactivated version of COVID-19 to create a DNA/mRNA type of vaccine.
In Canada, Dr. Chil-Yong Kang, from Western University in London, Ontario, is working on a vaccine using SARS-CoV-2. A Canadian company called Symvio (in conjunction with British Columbia and Dalhousie University) has proceeded to Phase I of its vaccine testing. Other universities that are actively working are McMaster, University of Alberta, British Columbia Saskatchewan and Manitoba.
There are additional vaccines being tested around the world. The Chinese company CanSino Bio, that started the first vaccine for COVID-19, is now proceeding to Phase 2 testing. The company has also applied to conduct trials in Canada. In the United States, a company called Moderna is now in Phase I of its vaccine testing, and are planning to add older adults to the trial as well. Another U.S. company called Inovio pharmaceuticals is also in Phase I of human testing. In Germany, BioNTech & Pfizer have worked together to develop a potential vaccine. They plan to include high-risk groups in their second phase of the trial, and also conduct testing in U.S., during May. In addition, pharmaceutical companies such as Johnson & Johnson and Sanofi are working together to develop a potential vaccine. In the UK, a vaccine was developed and was shown to be safe in humans, apart from minor side effects such as temporary headaches and sore arm after injection. Furthermore, Oxford University reported that this vaccine could be available as early as September.
In terms of progression to Phase III of testing, currently, only a Beijing-based company called Sinovac Biotech Ltd., was able to reach this phase. With help of WHO, the company plans to test the vaccine in regions of the world where the virus is spreading rapidly.
As you can see, countries around the globe are working together to find a vaccine for COVID-19. They are trying all the 5 types of vaccines mentioned above to find a vaccine as soon as possible. It is encouraging to see multiple organizations working together, each providing their specialty, speeding up this process.
All of us at Markland Wood Pharmacy hope you and your families are safe and healthy. We continue to take this journey with you and are available if you have any questions or concerns during this difficult time. When a vaccine become available, we will be there for you as well.
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