• Coronavirus vaccines are very effective in preventing hospitalization and death, but not as much against getting infected.
• Neutralizing antibodies generated in response to vaccines kick in nearly instantly and are therefore most effective in preventing infection.  However, with the coronavirus, they wane with time and are less effective against the new variants, including Omicron, BA.4, BA.5, BA.75, etc.
• B-Cells and T-Cells are also generated in response to vaccines. They take longer to act, usually sometime after an infection occurs.  However, they remain very robust over time and as new variants emerge, thereby protecting against severe and prolonged infection.
• Overall, vaccines continue to meet the fundamental Operation Warp Speed objective of protection from hospitalization and death.  This protection is very significant, but no vaccine is 100%.

It seems we are constantly bombarded with conflicting information about the effectiveness of the coronavirus vaccine.  Some highly credible sources within the medical community say it is still our best first-line defense whereas others say it’s useless. So, who do we believe?  My intent here is to offer the proper context to these apparently opposing statements, to help everyone understand the basics of how the vaccines work, – at least from a 50,000-foot view, and to connect the dots in understanding which aspects of the vaccine are working better than others and how that translates to the level of protection that we could/should realistically expect.

As of this writing, the current vaccines still protect well against hospitalization and death, even with the new variants.  However, they have always offered only limited protection from getting infected and getting sick.  This already marginal protection from getting infected/vaccinated has proven to wane quickly, and it seems to wane more quickly with nearly each new major variant.  Yet, by contrast, the protection vaccines provide against getting severely ill with COVID or dying of COVID is holding up quite well over time and with new variants.  So why the disparity between protection from initial infection and protection from hospitalization and death?

This partial success can be easily understood via a basic understanding of how the vaccines and our immune systems work.  In essence and as many of us are aware, vaccines simply “teach” our immune system to recognize a coronavirus infection and how to combat it.  Our immune systems protect us from various infections/illness by having the multiple components of our immune systems working together.  Fundamentally, what nearly all – if not all – vaccines do is exercise each of those components as separate components and in unison in the same or similar ways that actual infections do.

Thus, I will start with an overview of our immune systems, their components, and how they work.  Then, I will talk about the main types of vaccines and how they interact with our immune system.  From there, I’ll offer insight into connecting the dots and translating all of this into what we should expect and not expect of vaccines.

The Components of the Human Immune System and How They Work

Our immune systems are very complex with many components that work together to protect us.  The components can be grouped into the following two subsystems, which are closely linked and, therefore, operate in tandem:

Innate (non-specific) Response

The innate response provides a general defense against harmful germs and substances, hence the term non-specific.  We are born with a set of antibodies.  They are always present at some level and are dispersed within our blood and tissues.  They stand ready to attack an intruder on a moment’s notice.  Foreign substances that our antibodies directly attack are called antigens, and they include the types of germs that are common in our environment.  Since our antibodies are always present in our blood, they will immediately activate and pounce on a newly-introduced antigen, usually within minutes or hours.

This is just a top-level summary of this complex system/process.  For further information on how our innate immune systems work, please see National Institutes of Health (NIH) article “Autoimmunity: From Bench to Bedside”, Chapter 2 or other information sources

Adaptive (specific) Response

The adaptive response provides a coordinated immune response to disease-causing germs, or pathogens that invade our bodies.  Pathogens are live organisms that contain antigens in the form of proteins that are on the surface of a given germ cell.  They include bacteria and viruses, including the coronavirus.  The adaptive response engages B cells and T cells (see below for descriptions of each) in addition to the antibodies already present in our blood.  Our bodies recognize that a particular antigen should not be there, and it builds B cells and T cells that will remember how to fight a specific pathogen if it infects us again in the future.  The B cells and T cells provide a very strong response.  However, it can take up to several weeks after infection before they will fully recognize and fight a particular antigen.  As they kick in, the greater number of cells of a given pathogen, the greater the B cell and T cell response.  B cells also produce antibodies that are specific to a particular pathogen.

Hence, with an adaptive response, the antibodies provide an immediate response.  That immediate response is a combination of the antibodies present as part of the innate response plus those produced by B cells, which are part of an adaptive response.  The T cells also fight the pathogen very aggressively; however, like the B cells, it usually takes a few days for them to mount a significant response.

Now, I’ll provide a brief description of each of three major components.

Antibodies

As discussed above, antibodies provide the first-line of defense against an antigen/intruder.  Because they are always present, and their response is nearly instant.  It usually takes only minutes to just a few hours for our bodies to mount a substantial antibody response.  An antibody response occurs via phagocytosis, which is a major mechanism used to remove pathogens and cell debris. The ingested material is then digested in the phagosome, which is a vesicle ) (AKA membrane) formed around a particle engulfed by a phagocyte via phagocytosis. A phagocyte is simply a type of cell within the body capable of engulfing and absorbing bacteria and other small cells and particles.  This is what makes antibodies so effective in preventing and fighting an infection.

According to News Medical Life Sciences, phagocytes recognize and bind pathogens and then use the plasma membrane to surround and engulf pathogens inside the cell. As a result, a separate internal compartment (phagosome) is generated, which subsequently fuses with another type of cellular compartment called the lysosome. The digestive enzymes present inside lysosomes finally destroy pathogens by breaking them into fragments.  Some of these fragments are not digestible via phagocytosis.  These antigenic fragments are displayed on the surface of phagocytes, which are subsequently recognized and destroyed by cytotoxic T cells, which are described further below.

B Cells

B cells, AKA “memory” cells, are  a type of white blood cell, or lymphocyte that is activated when it encounters an antigen in the blood.  It then, in turn, formulates specific antibodies that will attack that particular antigen.  Hence, B cells are like the “recipe book” that remembers the specific antigen of the pathogen that was in the person’s blood as a result of a previous infection or vaccination.  After the infection, a low level of B cells will remain in the blood for a long time.  As soon as they encounter that same antigen again, they will go right to work producing the specific antibody that will attack that particular antigen.  Because B cells already know the “recipe” of the specific antibody, it usually takes much less time for the B cells to produce the needed quantities of that antibody that will annihilate the disease-causing pathogen.

T Cells

T cells are lymphocytes that come in two forms.  1) “helper” cells aid other immune cells by releasing cytokines.  Cytokines control and regulate the body’s inflammatory response.  2) “killer” cells, which directly attack and kill cells that are infected with a particular pathogen or cancer cell.  Combined, both types of T cells pose an extremely strong immune response.  However, like B cells, they take time to materialize after an infection.

Combined Response of These 3 Components

As you can tell from the above, antibodies, B cells and T cells all work together to fight off a given infection.  Again, the antibodies provide the immediate response, and the B cells and T cells provide a much stronger response, but it takes time for them to mount up that response, especially upon first-time exposure.

When a virus like the coronavirus infects us, it starts to quickly reproduce while, simultaneously, our immune system is ramping up its B cells and T cells to fight off.  This creates a “race” condition between the virus and our immune systems.

If there are enough antibodies present in the blood and tissues upon initial infection, they will annihilate – or at least neutralize – the virus/bacteria before it has a chance to replicate enough to produce symptoms.  This is what prevents us from getting sick at all – the best-case scenario.

However, in reality, such is often not the case.  The initial antibody response might slow down the spread of the pathogen but not be enough to stop it.  This leads to a race-to-the-finish-line situation between the pathogen spreading and the B cells and T cells mounting their response.  The further along the spread before these special lymphocytes kick in along with more antigen-specific antibodies produced by the B cells, the more severe the disease is likely to be.

How Vaccines Help

This is where vaccines are instrumental in fighting pathogens, including the coronavirus.  The vaccines introduce small amounts of either an attenuated (live but unable to reproduce) version of the pathogen, the dead pathogen (with antigens intact) or parts of the pathogen (again, with antigens intact).  Because the pathogen cannot spread, the aforementioned race condition doesn’t exist. Thus, it doesn’t matter how long it takes for the B cells and T cells mount a full-up immune response.  In the case of the coronavirus and several other vaccines, it takes about 2 weeks or longer to mount a full response, and that’s OK.

However, once a full-up response occurs the first time, a certain number of antibodies, B cells, and T cells specific to this pathogen remain in our blood.  The B cells already know the “recipe” of the antibodies and other responses needed to fight the pathogen.  Thus, the timeline for the B cells and T cells to mount their full response a second time is much shorter.  This helps a lot, in that it will all but guarantee that the immune system will win the race to avoid severe illness (assuming one has a healthy immune system), should our bodies actually become infected with the same pathogen.

Why Are Vaccines Against Some Diseases Are More Effective Than Vaccines Against Other Diseases?

The reason is twofold:

1. With some diseases, the antibody count in our blood remains high for longer periods. This is due to how our bodies react to the pathogen, regardless of whether it’s introduced via vaccine or actual infection.  This provides a more intense first-line immune response that is often enough to annihilate the disease – or at least impede it – before it can spread, thereby preventing any symptomatic infection.
2. Some diseases spread more rapidly than others.  For the slower spreading ones, the B cells and T cells often still have time to mount an adequate response to annihilate the disease before it causes symptoms.

How Does This Relate to The Coronavirus Vaccines?

Unfortunately, the coronavirus, itself, presents the worst of both worlds.  Our body’s antibody count drops off fairly sharply after infection or vaccine, and the virus multiplies/spreads extremely rapidly.  Thus, especially with the newer variants, the coronavirus often wins the race to symptomatic infection despite the vaccine’s best effort to preclude this.

However, thanks to the B cells being pre-programmed by the vaccine, the B cells and T cells still engage soon enough (in most cases) to prevent the coronavirus from spreading so much/so fast that it causes severe illness that requires hospitalization.  To me, this alone is a huge upside and is compelling enough for us to get the vaccine.

Conclusions

Coronavirus vaccines often don’t prevent us from getting sick with the coronavirus.  However, such illness is usually milder than it would be without vaccination and is much less likely to progress to the point that one must be hospitalized or worse.

This is really the primary objective of the vaccines and is why we can deem the coronavirus vaccine program, as developed under Operation Warp Speed, a success despite the fact that vaccines often don’t prevent illness altogether.

Upon approximately 2 weeks after receiving a coronavirus vaccine, we should not expect much protection from the common cold/flu like symptoms of the coronavirus.  However, we should know that we have significantly greater protection against severe infections that might otherwise land us in the hospital or worse. This is not enough protection for us to completely let our guard down, but enough to breathe a sigh of relief and resume our normal life activities.

Additional Information – Types of Coronavirus Vaccines

The Mayo Clinic website has a good description of the three types of the coronavirus vaccines.  Following is a brief summary:

1. mRNA Vaccine (most common in the US for the coronavirus): Genetically engineered mRNA is injected into our arms.  It “programs” our muscle tissue to produce the spike (AKA “S”) protein that is a primary antigen of the coronavirus.  Our immune systems recognize this S protein intrusion and mounts its response as previously described.  It’s important to note that the injected mRNA is not capable of replicating itself and that our bodies will eventually remove it from our bloodstream.  Thus, its presence and effects are temporary.  The Pfizer and Moderna vaccines are the two mRNA vaccines currently approved by the FDA for use in the US.
2. Vector Virus Vaccine:  Genetic material from the coronavirus virus is placed in a modified version of a different virus (viral vector), such as that of a common cold. When this viral vector gets into your cells, it delivers genetic material from the coronavirus virus that instructs our cells how to make copies of the S protein.  Our immune system reacts to these S proteins in the same way as it does to the S proteins resulting from the mRNA vaccine.  This is actually an existing/conventional technology that is often used for the annual flu shot.  The Jansen/Johnson & Johnson vaccine is the FDA-approved vector virus vaccine currently approved in the US.  However, it has proven less effective than the Pfizer and Moderna mRNA vaccines.
3. Protein Subunit Vaccine:   Subunit vaccines include only the parts of a virus that best stimulate your immune system. This type of coronavirus vaccine injects the harmless S proteins into your blood, which, in turn, triggers the same/similar response as the above mRNA and vector virus vaccines described above.  The subunit protein vaccine technology has a long-established history in fighting other viral diseases, including Hepatitis and Shingles.  The Novavax coronavirus vaccine was recently approved by the FDA for emergency use and is considered a good alternative to the mRNA vaccine for those who are more wary of the new mRNA vaccine technology.

Additional References Consulted (Not Cited Above)

• News Medical Life Sciences – “What are the Three Lines of Defense?”
• National Laboratory of Medicine – “How Does the Immune System Work?”

Note/Disclaimer

I am not a doctor nor an infectious disease expert.  This writing represents my best understanding and effort to explain vaccines and how our immune systems work at a level that’s understandable to most people.  It is not intended for the medical community, as they have far more advanced knowledge and information.  Thus, my technical/scientific descriptions might have certain gaps and/or perhaps even a couple minor inaccuracies.  However, I am most confident that I have accurately depicted the key points of how vaccines and our immune systems work in the context of how we should act on this information.