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COVID-19 Vaccination: What are the important highlights about immunity against COVID-19, that we should know? Read on.
COVID-19 affects everybody but elderly people are affected the most. As we grow older, our immune system weakens and so does our body response towards vaccines. Recently, researchers look into why this is happening to throw light on what it takes for a vaccine to work and work well. This is important to know, particularly for the group of people who need it the most.
Our Body’s Natural Defenses Against COVID-19
The Innate Immune Defense
When a virus enters the human body, be it Covid-19 or common flu virus, our body kicks in a “one-for-all” purpose defense. This line of defense is called “innate immune response”. Practically, the body releases large amounts of inflammatory and signaling molecules.
This is akin to sending a “SOS” signal to all military outposts in the nation. But, we don’t set fire to all the cities where we are dwelling during an enemy invasion. Yet, in our body, we do get a fever with all the circulating inflammatory molecules. This not only kill the enemies but also harm our own body cells in the long run.
That is why our innate immune system is never good enough as a single strategy to win the long term war between human body and viruses. We simply cannot afford to keep burning our farm lands every single time there is an intruder!
The Adaptive Immune Defense
On the other hand, the body invests in many intelligence centres that are located strategically throughout our body. These centres house many specialized immune cells that are capable of fast learning, have great communication skills as well as the ability to coordinate mass production at scale. It takes only about 7-14 days for these intelligence units to learn about an enemy’s weakness and design an effective weapon (antibody) that are fit for mass production even at distant sites. Hence, the name “adaptive immune system”.
Adaptive immune system activates white blood cells called lymphocytes. There are two broad types of lymphocyte responses—B cells which produce antibodies to neutralise the virus and T-cells or killer cells that kill the virus-infected cells.
Interesting Facts about T-cells
Did you know that viruses are like parasites that hide inside the host – unseen? If Superman starts with “S”, our heroes of the adaptive immune defense start with “T”. These T-cells are exceptionally good at identifying host cells that are infiltrated by viruses. In action, they quickly lock down the “spy”-infiltrated facility, capture it, and send the message across to intelligence units for development of preventive measures. Next time when our body encounters the same virus again, all the preventive measures are in place to stop the virus at doorstep.
This explains why a virus infection hardly lasts longer than 14 days. The virus would have been wiped out by our excellent immune defense. In this context, anyone with COVID-19 infection, who self-isolates for at least 2 weeks, would hardly have much virus left to spread to others.
Age and Immune Defense
COVID-19 can cause severe infection in elderly people. On a quest to find out why, researchers are paying close attention to how the immune system of older patients functions during an acute COVID-19 infection.
Among people older than 65 years with acute COVID-19 infection, those with well-coordinated adaptive immune response tend to fare better. However in most cases, the adaptive immune defense weakens as we grow older. For instance, the pool of T-cells decreases over years. Also, the amount of antibodies produced may not be enough to kill all the invading viruses. This leads to a delay in activating the adaptive arm of defense. Worse still, the rate of viral replication may be faster than the rate at which the body is killing it.
As such, without an effective adaptive arm of defense against COVID-19 in elderly people, the virus stays alive in our body. In response, our body reacts more aggressively with an innate immune defense that kills not only the viruses but also our own cells. Eventually, this leads to burnout and the virus win the battle.
Photo by Pascal van Gerven from Flickr
COVID-19 Vaccination Strategy
How Vaccination Work
Vaccines work by provoking an immune response when exposing material from the infectious agent eg SARS-COV-2 virus to the body.
Vaccines use different methods depending on the technology: from harmless proteins of the virus, to modified virus (vector) to biological virus material (messenger RNA). Recent vaccine announcements from Pfizer & Moderna are messenger RNA vaccines. These vaccines present the biological material to the immune system, so our immune cells get a chance to learn about it. It then triggers the body’s immune system to begin the infection-fighting process, bringing out both types of immunity by the B and T cells.
In addition, our immune system secures these blueprints for antibodies production by dedicating the task to unique memory cells. These memory cells are able to renew themselves to replace any dead antibody-producing cells etc. Thus after vaccination, upon the next encounter with the same virus, before they get a chance to infect our cells, the virus would be deactivated, killed or blocked.
The Strategy Road Map
In this sense, COVID-19 vaccination is probably the best way to create long term immunity in the fight against the virus. For example, with the advent of small pox vaccine, mankind almost eradicated small pox infection worldwide. Yet, there are still concerns surrounding COVID-19 vaccination, especially in older people.
Given the fact the virus is more likely to infect older people and more seriously, this is the group who would benefit the most from COVID-19 vaccination. However, if the adaptive arm of defense gets weaker and less coordinated as we age, the body may not respond well to vaccination. The amount of antibodies produced may be inadequate to prevent another COVID-19 infection. It is also possible that such immunity may not last for a long time due to smaller pool of immune cells at work.
To date, clinical data show that people who recover from COVID-19 infection have rather strong immunity against the virus, including older patients.
Meanwhile researchers are also deepening their understanding on human immunity relating to COVID-19 vaccination. The research shows that ideal vaccine candidates should bring forth a broad immune response, including antibodies, T cells, and memory cells to provide protective immunity.
Photo by today mynews from Flickr
Conclusion
In the face of the pandemic, progress in vaccine development is hampered by our limited understanding on effective immunity. This is particularly important to ensure COVID-19 vaccination efficacy in the elderly, the vulnerable group. Further research would be necessary to move us closer towards a successful COVID-19 vaccination. A successful vaccination strategy is imperative for us to eventually win the war against the Covid-19.
Read More:
Obesity and COVID-19: Danger of Hospitalisation & Death Risks
Surviving the Long Road to Recovery After COVID-19 | GetDocSays
Looking at the Bright Side of COVID-19 | GetDocSays
References:
1. Moderbacher CR, Ramirez SI, Dan JM, Grifoni A, Hastie KM, Weiskopf D, et al. Antigen-specific adaptive immunity to SARS-CoV-2 in acute COVID-19 and associations with age and disease. Cell. 2020; DOI: 10.1016/j.cell.2020.09.038.
2. Koff WC, Williams MA. Covid-19 and immunity in aging populations – a new research agenda. N Eng J Med. 2020 Aug 27; 383:804-805. DOI: 10.1056/NEJMp2006761.
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by Chang Xian
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