15
Jul

The spread of COVID-19 has caused unprecedented disruptions around the world. Economies have slowed, many sectors (especially those related to tourism and the hospitality industry) have been negatively impacted to severe degrees, and many nations are facing unprecedented levels of unemployment. The impacts of this pandemic are being felt far and wide, and the timeframe for recovery once this virus is under control will be a long one. As we pass the half-year mark of combating COVID-19, there are a number of nations that have appeared to have the virus under control, with case numbers either not increasing or growing at a significantly reduced rate. These countries have begun lifting restrictions and allowing their citizens to return to a state of pseudo-normalcy, what many are calling a “new normal”; social-distancing in place, many still work from home, and most hospitality-related businesses running at reduced capacity.

covid-19 vaccine development

 

As the restriction lifting continues, there is mounting fear of a viral 2nd-wave. Efforts are being made to lessen the chance of this happening, and one such strategy is the extensive testing of the population with COVID-19 IgM/IgG Rapid Tests. These test for the presence of antibodies that would be produced by people either currently fighting the virus or have recovered from it. However, the only true solution that we have for this pandemic, other than letting it run its course (which would result in millions of deaths), is the development of a vaccine. To discuss vaccines, we should first discuss how the body fights back against infection-causing pathogens.

How does your body fight pathogens?

When a pathogen enters your body and is identified by your immune system, your body will produce proteins called antibodies that will fight back against the intruder. Once these antibodies are produced and your body fights off the pathogen, your immune system is now equipped to effectively fight against this specific pathogen.

The beginning of an infection, when you are visibly sick and experiencing symptoms of the illness caused by that pathogen, is when your body is beginning to fight and develop these antibodies. The problem with this approach is, if the infection is strong enough, you might die before your body can develop these antibodies. Thus, this is where vaccines come in.

What do vaccines do?

If your immune system fighting the pathogen is akin to going into a battle or a fight, a vaccine can be considered immune system training or target practice. There are a few types of vaccines, which we will briefly discuss here, but the basic premise for all of them is that the vaccine allows your body to simulate a real infection. This is done by exposing your body to either a significantly weakened or killed version of the pathogen, or a specific part of the pathogen (like a protein, sugar, or cell portion), so that your body’s immune system is activated into producing the appropriate antibodies. Thus, if the vaccine does its job, your body will be well and ready to fight the real pathogen if it encounters it in the wild.

Types of Vaccines

There are a few different vaccine types available, with each having their advantages and disadvantages.

Attenuated Vaccines:

These vaccines are made up of attenuated (weakened) but still viable (alive) pathogenic particles. As such, the immune response is much stronger, activating all aspects of the body’s immune system, meaning that booster shots are typically not required. If you need a strong vaccine, attenuated is the way to go. Issues related to this include potential complications arising if in the very rare case that the weakened virus mutates back to a virulent strain, and potential health risks in those who are immunocompromised. An additional issue would be the more stringent storage conditions in order to keep the pathogen alive; this can include the necessity for fresh media or storage solution, as well as the requirement for refrigeration. This can be an issue when extended transportation and storage is required, especially to remote locations. Examples of attenuated vaccines include those used for measles, smallpox, chickenpox, and yellow fever.

Inactivated Vaccines:

These vaccines are made up of previously viable (living) pathogens that have been inactivated (killed), with this being done by heat or chemical means. Benefits of this vaccine type is that, in comparison to an attenuated vaccine, living pathogen is not introduced into the body, and storage conditions are much less rigorous allowing for easier transport. One disadvantage is that these vaccines typically do not produce as strong of an immune response as a vaccine containing a weakened form of the virus, thus booster shots are usually required. Examples of inactivated vaccines include those used for Hepatitis A, seasonal Influenza, and Polio.

Conjugate, subunit, recombinant, and polysaccharide vaccines:

These types of vaccines depend on the use of only a part of the pathogen, not the whole pathogen, to generate an immune response. These parts could include glycans and sugars that would be expressed on the outside of the pathogen, pathogenic surface proteins, or parts of the capsid (outer coating) of the pathogen. The type of piece that is used will depend on the pathogen and how the body’s immune system responds to these pathogens. Benefits of these include a very strong immune response, as only the component of the pathogen that generates a response is added, and these vaccine types do not cause additional complications in those with other health issues or compromised immune systems. Disadvantages include the potential requirement of booster shots to keep up immunity over time. Examples of pathogens that utilize this type vaccine include Hepatitis B, HPV (Human Papillomavirus), and shingles.