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The COVID-19 pandemic has resulted in a huge allocation of resources towards producing solutions, from identifying life-saving drugs, to monitoring the spread of the virus and, finally, to preventing infection with vaccines.
As a medical scientist, I study how the virus evolved during the pandemic, as any changes in the virus could also change the effectiveness of current treatments. On November 9, Pfizer announced preliminary trial results showing that a vaccine developed with BioNTech was about 90% effective. This was followed up nine days later with the final study results and two months of safety data, indicating an efficacy rate of 95%.
READ MORE: Pfizer requests approval of emergency coronavirus vaccine in the United States
Pfizer announced on November 18 that it intends to file for emergency clearance with the US Food and Drug Administration.
Meanwhile, on November 16, Moderna announced preliminary results for its vaccine, which was developed with the U.S. National Institutes of Health, which also indicated an efficacy of around 95 percent.
This is good news, but we need to understand what it means so that life can finally return to normal.
DNA, messenger RNA and proteins
Both Pfizer and Moderna vaccines are mRNA based. In each of our cells, DNA produces messenger RNA (mRNA) containing the blueprints for making proteins. It’s called messenger RNA because it carries that information to other parts of the cell, where instructions are read and followed to make specific proteins.
When a patient is injected with mRNA in a vaccine, their cells use the information in that mRNA to create a protein – in this case, a version of the coronavirus spike protein that causes COVID-19. The immune system recognizes that protein as a signal to make antibodies and immune cells.
An mRNA vaccine has some advantages for mass vaccination. It can produce robust immunity, it can be produced quickly at low cost, and like inactivated and subunit vaccines, it is impossible for anyone to develop the disease.
Building immunity
This vaccine has the potential to protect many people from this devastating virus. When a vaccine is said to be 90% effective, this means that if 100 people received the vaccine and were then exposed to the virus, 90 are unlikely to get sick. While 10 would be at risk of developing the infection again, vaccine protection is not all or nothing. These 10 individuals may have milder disease than someone who did not receive the vaccine.
It takes time for the immune system to prepare to fight infections. Think about building immunity against SARS-CoV-2, the virus that causes COVID-19, like preparing to run a marathon. First, the runner must register, as well as the immune system must be exposed to the infectious agent. Hence, they need to increase stamina. For the immune system, this means producing antibodies and immune cells. Finally, they run the marathon – the strengthened immune system now removes the infectious agent from the body or prevents it from doing further damage.
In both Pfizer and Moderna clinical trials, subjects received the vaccine in two doses, three or four weeks apart, respectively. This is how long it takes for the stimulated immune system to produce significant protection. A booster vaccine was given to produce even more antibodies and immune cells. As for the marathon example, it’s like doing a practice marathon around three weeks of training. The runner will do better than he would on day one, but more training is likely still needed. The booster vaccine provides that extra training.
The beginning of the end
Should we expect the pandemic to end once a vaccine is available for public use? Not exactly. A vaccine will not be perfect and it takes time for the immune system to be ready to protect us.
Furthermore, it is possible that vaccines are less effective than quoted. Clinical trials are carefully planned, but it is possible that the virus has evolved enough since vaccines were designed to provide fewer benefits. It will also take time for sufficient vaccine to be produced and administered for the population to achieve herd immunity.
Masks and social distancing will still most likely be needed throughout 2021 because it takes time to carry out projects on such a large scale. We cannot expect herd immunity from our neighbors getting sick to bring the world back to normal, even while the neighbors are receiving vaccines. The human cost is unacceptable, and the virus is too contagious to produce significant results unless 67% of the population is infected, with many people dying by then and beyond.
We are in a frightening time, but we have reason for hope. The news of Pfizer and Moderna vaccines is good news and could potentially set the world back to something more normal. We must not forget that it will take time and we will all work together. Masks and social distancing are our reality right now and will remain so at least until next year. We must persevere with these measures, even when we find them frustrating. There is a light at the end of the tunnel and we can all reach it if we work together.
Julian Daniel Sunday Willett, PhD student, quantitative life sciences, McGill University
This article was republished by The Conversation under a Creative Commons license. Read the original article.
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