The world is now on a race to find a vaccine to the SARS-COV-2 virus that causes the COVID-19 pandemic. According to the Coalition for Epidemic Preparedness Innovations which maintains an overview of the global landscape of COVID-19 vaccine development activity, there are a total of 115 vaccine candidates being developed all over the world as of 8 April 2020 [1]. Among them, 78 are in active development. While most of these vaccine candidates are still in the exploratory or preclinical stage, five of them already began testing in humans [1].
Why the vaccine?
A vaccine is a substance that can stimulate the body’s immune system to produce antibodies against the infectious agent that causes a disease. The world has seen the benefits of vaccines since the discovery of smallpox immunisation by Edward Jenner in the late 18th century. The development of vaccines and population immunisation programme is credited for the prevention and eradication of many diseases including smallpox, polio, measles, malaria, tetanus, sepsis, and many more [2]. As such, vaccines have become a mainstay of the medical and public health approach for the prevention of infectious diseases [3]. Not surprisingly, vaccine development is among the top priority in the world’s response to the current pandemic.
How the body fights the coronavirus?
To understand how the vaccine works, we need to learn how the body is organised against any infectious assault. There are two main branches of the immune system: innate and adaptive.
The innate immunity consists of many types of white blood cells such as the macrophages and neutrophils. There are akin to the patrolling police in the body, always looking out for any potential danger. The moment any infectious agent is detected, these white blood cells will quickly rush to the site of infection and ‘swallow’ up and destroy the infectious agent [4].
However, the innate immune cells can only recognise some characteristic signatures that shared among many pathogens. They are unable to detect a new pathogen such as the novel coronavirus to mount any effective response. We know that many infected people continue to show no symptoms during the initial stage of the infection. Even though the virus is already starting to survive and replicate in their respiratory system. The innate immune cells will still be triggered subsequently after infected cells were destroyed by the coronavirus. Finding foreign proteins in the debris of the dead cells, the innate immune cells will respond in force to destroy the infected cells and causing acute inflammation in the process [5]. The patients may thus develop symptoms such as cough, fever, and pneumonia in more severe cases [5].
A type of innate immune cells, called the antigen-presenting cell (APC), initiates the adaptive immunity. The APC will ingest the coronavirus and present a portion of the protein sequence of the virus to the T-helper cells of the adaptive immune system. The T- helper cells, in turn, will trigger the B-cells to generate antibodies that can stop the replication of this specific virus and cytotoxic T-cells that can recognise and destroy the coronavirus. The body can then effectively eliminate the coronavirus at this stage and will recover from the disease. Some of the T- and B-cells generated in this response will become ‘long-lived” to preserve the memory of the coronavirus. These cells will continue to patrol the body and launch an immediate attack against any similar virus they encounter. They are making the body immune against the same infection in the future. Hence, immunity is ‘acquired’ [6].
The making of vaccines
However, the time-lapse between the initial infection and the eventual activation of the adaptive immunity can be too long for some people. The inflammatory cascade associated with the response of innate immunity may lead to complications such as the acute respiratory distress syndrome which can be life-threatening [5]. Therefore, it will be beneficial if the body can acquire immunity through some other means before the actual infection, which is the purpose of having a vaccine.
A vaccine is a relatively harmless substance that mimics the recognisable proteins of the actual virus. The idea is to inject such a substance into the body to initiate the adaptive immunity process. If the body is subsequently infected by the actual virus, the memory B- and T-cells that are already in place can quickly eliminate the infection before it can cause any serious damage.
Currently, scientists are exploring the use of many different substances for this purpose. Among them include weakened or inactivate coronaviruses; portions of the coronavirus’s gene or its protein fragments; and modified forms of another virus [6]. Only time will tell whether which of these approaches is successful.
Are vaccines infallible?
Vaccines may not always work though. The targeted pathogens can mutate to evade the body’s adaptive immunity. SARS-COV-2 is a type of ribonucleic acid (RNA) virus. RNA viruses can quickly replicate due to their simple structure. However, a mutation in the genetic codes can also quickly occur after many copies. Cumulative changes in the genetic materials of RNA viruses can make them no longer recognisable by the immune system [7]. Hence, even a previous immunised person can be reinfected by a mutated form of the same RNA virus. Take the example of seasonal influenza, the immunity rendered through its vaccine is only short-lived, and many have questioned the effectiveness [7].
The availability of vaccines does not eradicate influenza. It was estimated that about 294 000-518 000 people died due to complications associated with influenza globally each year [8]. The coronavirus is like influenza virus in many ways, and hence, even if a vaccine is found, the question is how effective and long-lasting the effect can be? It will be naïve to assume that a coronavirus vaccine can be a magic bullet that ends the COVID-19 disease.
Boost your immune system
Let us not pin our hope on the eradication the COVID-19 on any vaccine. It is good to have vaccines for protection for the high-risk group, especially older adults with multiple chronic conditions since they are vulnerable to respiratory complications. Keep in mind that about 80% of the patients infected by the COVID-19 on disease showed only mild symptoms of flu and cough [9]. It is more important to boost the immune system naturally through healthy diet and lifestyle, to be impervious to the disease. Eat a balanced diet with lots of dietary fibres, vegetables, fruits and lean proteins. Quit smoking, exercise daily, reduce stress, and maintain a positive outlook in life. These are the formula to protect against any disease.
Conclusion
One depends on the body’s immune system to fight against disease-causing pathogens like the coronavirus. Although the world is racing to find a suitable vaccine for SARS-COV-2 virus, it is unrealistic to expect any vaccine can fully eradicate the COVID-19 soon, if not ever. It is essential to maintain a healthy body with a robust immune system, our natural protection against coronavirus.
References
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[9] I. Thevarajan, K.L. Buising, B.C. Cowie, Clinical presentation and management of COVID-19, Med. J. Aust. (2020). https://www.mja.com.au/journal/2020/clinical-presentation-and-management-covid-19 (accessed 15 April, 2020).