When someone inhales respiratory droplets loaded with SARS-CoV-2 there are many possible outcomes for each of the viral particles. We can think of these viral particles as being soldiers of an invading army. After the viral particles land in our respiratory tract, they will first encounter a general defense system. This general defense system is like having coils of razor wire strung across the border; with traps set up to snare invaders that get through, and sentry guards posted to identify the intruders and call for backup. If the number of viral particles that are taken into the body is small - then the first line of defense might be enough to keep the virus from getting into enough cells to cause a problem. A person might have no symptoms.
If the virus gets past the general defense system, one of the next potential lines of defense are antibodies. These are complex protein structures the body manufactures. Antibodies can be thought of as squads and battalions of cloned foot soldiers with one job. If you have enough of the right kind of foot soldiers ready to go and the invasion is not overwhelming; your body is going to have a good chance of keeping the virus in check. If you have been recently vaccinated, you will have high levels of antibodies that bind to the part of the virus it uses to get into your cells. If you have not been recently vaccinated or infected your body will start the long complex process of making antibodies against SARS-CoV-2. It will however take several days for your body to produce adequate numbers of antibodies to keep the virus from entering into our cells.
Antibody levels do start to wane after infection or vaccination however your body has “memory B cells” that can be activated by vaccination or infection to start making antibodies specific to the virus.
SARS-CoV-2 is continuously changing. As the virus changes the targets the antibodies match up to change. Fortunately the virus has not changed so much that previous vaccine formulations or infections by previous versions of the virus still provide some degree of protection against severe disease. For people who have not had an infection or vaccine for several months - updated vaccines that are better targeted to the current variants will improve the odds. The updated vaccines will reduce a person's risk of infection and serious illness. There is good evidence that updated vaccines also reduce the risk of transmission.
Antibodies are like clones of soldiers built to battle specific vulnerabilities of an invader. The vulnerable part of SARS-CoV-2 virus is the "spike protein" - the virus needs this to get into your cells. If you have enough antibodies binding to the right parts of the spike protein it can't get into your cells efficiently. The more sets of soldier clones you have ready to go and the better those soldiers match the vulnerable parts of the invader - the faster and more completely you will beat back the invader. This is what an updated vaccine can do for you. The updated vaccines are specifically designed to match the changes that have occurred in the spike protein of SARS-CoV-2.
Antibodies are only one part of your body’s defense system. We have an array of other weapons. This includes specialized immune cells that are the tanks, heavy artillery, cruise missiles and smart bombs of the immune system. Lymphocytes are a key part of this system. There is evidence of improved lymphocyte function after COVID-19 vaccination.
Lymphocytes are a subset of white blood cells that are important in fighting viral infections. There are several different subsets of lymphocytes with a wide range of distinct duties. For example, Cytotoxic T cells are trained to destroy cells that are infected with a specific virus. They get this training after vaccination or infection. Another set of lymphocytes needs no training and are aptly named “natural killer cells” (yes, that is the true name for them). Natural killer cells are like roaming assassins looking for anything that is bad. Natural killer cells as they circulate through the body can sense when a cell is just not right. They can tell if a cell is a bacterium, has been infected with a virus or is a cancer cell. They can cause a cell that does not look right to die.
There are also other subsets of lymphocytes that don’t directly play a part in killing but are critically important to the functioning of the immune system. You can think of these cells as being the military providing essential direction and support. These lymphocytes can activate and encourage squads of killers. They are essential in the creation and production of the cloned foot soldiers manufactured by the B Cells. They direct the overall battle plan and stimulate parts of the immune system. Regulatory lymphocytes can also cause contraction of units of the immune system putting what is not needed back into sleeper cell mode.
In COVID-19 the most common lab abnormality is a low lymphocyte count. One study showed that about 90% of patients admitted to the hospital for COVID-19 have low lymphocyte counts. This would seem counterintuitive since lymphocytes are important in fighting viruses - you would expect your body to be making larger than normal numbers of lymphocytes.
While the reasons why people with COVID-19 have low lymphocyte counts is not clear, we do have some ideas. There are probably several reasons why this is the case. There is evidence the virus can directly infect lymphocytes. The low lymphocyte counts may also in part be due to a burnout or exhaustion of lymphocytes during infection. The mechanisms are unclear but there is also evidence of virus induced dysregulation of the immune system. There is also evidence that for many people their immune system is messed up for some time after they have been infected with the virus.
Just like in war, communication is key. Weapons and troops need to be deployed strategically. Artillery shells, bombs and missiles may destroy the enemy but there may be unacceptable collateral damage.
Our immune system cells communicate with each other in a number of ways. Cells that discover the invader will ingest and then present the invader or parts of it on the surface of their cell membrane to lymphocytes. Cells also use substances called cytokines to talk with each other.
Like in a battle - things get frantic, and effective communication breaks down, coordination fails. When this happens in people with COVID-19 we call it a “cytokine storm”. At this point your body’s immune system is not working in a deliberate coordinated manner. The body is panicking, throwing grenades in the general direction of the enemy, shooting without looking and using shotguns instead of rifles.
If the body survives the invasion it may take weeks or months to recover and rebuild. Your country may have survived the invasion but there may be lasting structural damage and many casualties. The old adage: “what does not kill you makes you stronger”, just isn’t true when talking about serious infections. You might survive your COVID-19 infection, but studies have shown that this does not completely protect you against being hospitalized from a subsequent infection and you may have lasting symptoms and disability for months. Vaccination provides safer protection since the immune system works in a more controlled manner. It makes sense to me that our immune system is going to do a better job when the body is not under attack from the virus.
Go to vaccines.gov to find a location to get vaccinated.
All statements in this article should be attributed to myself, not any organization I represent or my employer. This article presents a medical perspective - not a statement intended to be for or against any public policy or politician.
Russ Coash, PA-C
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