Covid-19, the virus known to have started in Wuhan at the end of 2019, has been spreading rapidly worldwide around February 2020. As the spread continued, vaccinations began in each country, starting with the first vaccine Pfizer that was urgently approved. In the process of vaccination, concerns about side effects and numerous rumors were produced.
Also, some may be feared about the consequence of the ‘Gradual Return to Normal’ policy and got a booster shot, yet knowing how it protects from the virus. So let's learn and figure out questions and concerns about the virus; get a balanced perspective by looking at it scientifically and fundamentally rather than just knowing it phenomenally and conclusively being vague.
How does Vaccine work?
WHO explains that when a pathogen(a bacterium, virus, parasite, or fungus that can cause disease within the body) does infect the body, our body’s defenses, called the immune system, are triggered and the pathogen is attacked and destroyed or overcome.
Each pathogen is made up of several subparts, usually unique to that specific pathogen and the disease it causes. The subpart of a pathogen that causes the formation of antibodies is called an antigen. The antibodies produced in response to the pathogen’s antigen are an important part of the immune system. You can consider antibodies as the soldiers in your body’s defense system. Each antibody or soldier in our system is trained to recognize one specific antigen. We have thousands of different antibodies in our bodies. When the human body is exposed to an antigen for the first time, it takes time for the immune system to respond and produce antibodies specific to that antigen.
In the meantime, the person is susceptible to becoming ill. Once the antigen-specific antibodies are produced, they work with the rest of the immune system to destroy the pathogen and stop
the disease. Antibodies to one pathogen generally don’t protect against another pathogen except when two pathogens are very similar to each other, like cousins. Once the body produces antibodies in its primary response to an antigen, it also creates antibody-producing memory cells, which remain alive even after the pathogen is defeated by the antibodies. If the body is exposed to the same pathogen more than once, the antibody response is much faster and more effective than the first time around because the memory cells are at the ready to pump out antibodies against that antigen.
This means that if the person is exposed to the dangerous pathogen in the future, their immune system will be able to respond immediately, protecting against disease.
Vaccines contain weakened or inactive parts of a particular organism (antigen) that trigger an immune response within the body. Newer vaccines contain the blueprint for producing antigens rather than the antigen itself. Regardless of whether the vaccine is made up of the antigen itself or the blueprint so that the body will produce the antigen, this weakened version will not cause the disease in the person receiving the vaccine, but it will prompt their immune system to respond much as it would have on its first reaction to the actual pathogen.
Some vaccines require multiple doses, given weeks or months apart. This is sometimes needed to allow for the production of long-lived antibodies and the development of memory cells. In this way, the body is trained to fight the specific disease-causing organism, building up memory of the pathogen so as to rapidly fight it if and when exposed in the future.
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There are diverse kinds of vaccines but the purpose to have prior knowledge is common. Let's find out how each type of vaccine works in detail.
VACCINES
Classic version: Inject weakened antigens.
Inactivated vaccine (ex.Sinovac)
: After mass cultivation of the virus, it is deactivated and injected into the body to recognize antigens.
Protein vaccine (ex. Novavax)
: Its principle is to inject antigenic proteins are into the body. Novavax analyzed the RNA of the spike protein and succeeded in mass production of the spike protein through gene recombination technology and deformation of the DNA of moth cells.
mRNA vaccine (ex. Moderna, Pfizer)
: To produce spike proteins in our bodies, inject mRNA, a blueprint for making spike proteins. There are technical difficulties such as the structural instability of RNA, the body recognizes external RNA as an enemy, so utilization of the disguising strains used by the coronavirus is needed. To this end, RNA was properly deformed and was packaged with lipid nanoparticles to successfully manufacture. Although there still is a disadvantage that a cold chain is required to overcome the structural instability of RNA, it can be produced in the shortest time since it does not require a separate culture process.
Virus vector vaccine (ex. AstraZeneca, Janssen)
: After reassembling DNA based on the spike RNA of the coronavirus, it is inserted into the DNA of the adenovirus that pathogenicity and reproductive availability are eliminated to secure stability. The secure adenovirus acts as a carrier of spike proteins, so we call it a Virus vector vaccine. However, when a virus is used as a carrier, there is a possibility that the immune system detects and destroys the carrier as a virus.
Vaccines using DNA vectors can be stored at higher temperatures than RNA. Thanks to these characteristics, Janssen used vector vaccines to successfully produce vaccines for the Ebola virus that occurred on a large scale in Congo lately.
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Side effects
Like any vaccine, COVID-19 vaccines can cause mild, short-term side effects, such as a low-grade fever or pain. Most reactions to vaccines are mild and go away within a few days on their own. More serious or long-lasting side effects to vaccines are possible but extremely rare. Vaccines are continually monitored for as long as they are in use, to detect rare adverse events and implement approaches to limit their occurrence.
Reported side effects to COVID-19 vaccines have mostly been mild to moderate and short-lasting. They include : fever, fatigue, headache, muscle pain, chills, diarrhea, and pain at the injection site. The chances of any of these side effects following vaccination differ according to the specific COVID-19 vaccine.
WHO explains the side effects as above, but people are still anxious about vaccination. In addition to side effects, there is a concern that the breakthrough infection and virus mutation may not be effective against vaccination.
Breakthrough infection refers to a case of infection even after being vaccinated. As can be seen from the news that 20 out of 47 confirmed cases (in September at Soonchunhyang University Seoul Hospital) are breakthrough infections, the vaccine does not prevent perfectly from infection. According to CDCs, the COVID-19 vaccine is effective in preventing most infections but still, a breakthrough infection is expected. Those who have completed the vaccination are less likely to become more severe than those who do not get vaccinated and get COVID-19 even if a breakthrough infection occurs.
What if virus mutation neutralizes vaccine effectiveness?
Mutations can occur in directions 1) unfavorable to the spread of the virus, 2) in directions that do not affect it, or 3) in favorable directions. Although biological evolution occurs in a direction favorable to propagation, memory cells still exist unless the spike protein itself is deformed, so the vaccine’s effectiveness that enables rapid antibody production remains.
What if the evolution in a direction favorable to the deformation and propagation of spike proteins is faster than the speed of development of vaccines? According to the Paper ‘Nature’, it is not. It is said that ‘We do not identify a single recurrent mutation in this set convincingly associated with increased viral transmission. Instead, recurrent mutations currently in circulation appear to be evolutionary neutral and primarily induced by the human immune system via RNA editing, rather than being signatures of adaptation. At this stage, we find no evidence for significantly more transmissible lineages of SARS-CoV-2 due to recurrent mutations.’
Recent issues
Starting from November this year, Korea is now in the ‘With-Corona’ scheme. However, soon after, a growing number of countries, including Korea, have reported confirmed cases of the Omicron variant, Hence, over 70 countries and territories have imposed travel restrictions from several African countries following the discovery of the variant.
The Omicron variant is perceived as a crisis since it has twice more genetic viruses in the spike protein compared to the delta variant. Based on this factor, Moderna's CEO said he thought the Omicron variant would have an impact on the vaccine’s efficacy. The transmissibility is estimated to be significant considering the spread of the mutant virus in South Africa. Up to now, however, it is analyzed that the severity has not been high so far. Moreover, the prevailing opinion is that treatments for COVID-19 will be effective for Omicron because they prevent replication of the virus itself.
The rapid biological evolution of viruses bothers humans, but we humans can respond to viruses through cultural evolution that viruses do not have. Both humans and viruses have expanded their ability through genetic evolution, but humans can take the lead in another way beyond the limits of genetic evolution. It is cultural evolution, in other words, quarantine. Active vaccine cooperation, social distancing, and wearing masks are key to solving problems that human biological genes cannot overcome.