Abstract: As the vaccines for COVID-19 have been successfully developed, some people may shilly-shally about whether to get vaccination. This article introducing several types of vaccines and explaining their safety may give you an answer.
In 2020, the new type of coronavirus pneumonia, COVID-19, is raging, and human beings are still living in a panic with this huge threat, Up to now, COVID-19 has caused more than 100 million people to be infected worldwide, and the number of related deaths is as high as over 2 million. These are all stimulating our fragile nerves, and in the short term, it seems that we should pin our hopes on the vaccine. So what should we know about the COVID-19 vaccine?
① Live attenuated and killed vaccine: As the most mature production process, it has the advantages of fast research and development, less requirement to evaluation and storage. The main disadvantages are that it requires multiple inoculations and the production cycle is relatively long.
②Protein subunit vaccine: This vaccine is developed quickly, with mature technology and less adverse reactions, but it also has many shortcomings, such as weak immune effect and long production cycle.
③Adenovirus vector vaccine: This method has high gene delivery efficiency and can produce a strong immune response, but its shortcomings are also obvious—the technical requirements for virus production are very high and security risk is also a problem.
④mRNA vaccines: This type of vaccine is controversial and there are no products on the market yet. The main advantage is that it can produce an immune response quickly, the industrial production is relatively simple, which is more in line with the needs of mass production.
⑤DNA vaccines: Like mRNA vaccines, the technology is relatively immature. This type has the advantages of fast research, development and production. The disadvantages are that they are affected by expression efficiency and there are potential risks of active integration into host DNA.
Vaccines can make us safer in the thread of the coronavirus, but there are also some problems, such as the inconsistent evaluation criteria of vaccine effectiveness and diagnostic criteria, as well as clinical trial population composition, number of people participating in clinical trials, adverse reaction statistics, and protection rate calculation methods. It is necessary to establish international unified parameter indicators for standardization.
Currently, the Centers for Disease Control and Prevention (CDC) has proved two mRNA vaccines—Pfizer-BioNTech for people over 16 years old, and RNA-1273 from Moderna for those over 18 years old, which means these two kinds of vaccines are of assured safety. However, the official does mention reactogenicity including local symptoms ( pain, swelling, erythema at the injection site, localized axillary lymphadenopathy on the same side as the vaccinated arm), and systemic symptoms (fever, fatigue, headache, chills, myalgia, arthralgia).
The novel coronavirus, SARS-CoV-2, enters the cell mainly by the combination of the spike protein and the cell membrane. The spike protein is like a sword, inserted into the scabbard of the ACE2 receptor on the cell membrane. This protein is flexible and can swing freely on the surface of the virus, allowing the virus to be more flexible. Therefore, the S protein as a key site has received extensive attention, and the current vaccine development is related to the S protein.
Recently, mutant viruses discovered in the United Kingdom and South Africa are mainly concentrated on spike proteins, and the occurrence of mutations makes it easier for the virus to enter the cell and complete the invasion. From the current results, the mutation site of the virus does not affect the effect of the vaccine; follow-up experiments are also underway. Scientists are also comparing the sequences of the two viruses and conducting animal experiments to reveal the effectiveness of vaccines.
Vaccination can give individual protection capabilities to SARS-CoV-2. When the immunized population of a country or region reaches about 70%, herd immunity can be realized. Thus the official recommends vaccination to medical and health, customs inspection, imported products, military police, and social security related practitioners first, and then to the public.
A perfect vaccine should be safe enough, not cause other complications, and can be widely used in different populations; it should also have sufficient efficacy, which lasts a long time. Economic evaluations, and cost performance are also key factors.
Vaccines, as the most effective means of preventing COVID-19, have gathered global wisdom. However, there is no vaccine that can fully meet the above standards. With the advancement of technology, there are still many routes being continuously developed and improved. What we have to do is to use all routes of vaccines and build a "protection wall" together with the concerted efforts of various countries, so that we can early take off the mask and take a breath of fresh air.