This is part one of two posts about vaccines. A SARS-CoV-2 vaccine is sorely needed and, fortunately, as of June 4th there are 137 vaccines against the virus that are in development across the globe, and 17 are in human trials. This post is about the types of vaccines and how they work. Part two will be about the testing and approval process for vaccines and other drugs.
The first vaccine was developed by English doctor Edward Jenner. He noted that milkmaids who had been infected with cowpox tended not to get smallpox. He injected people with cowpox and it protected them from smallpox and the first vaccine was born.
All vaccines work the same way — they cause your body to create antibodies specific to a virus so that when your body is infected with the virus your immune system is ready to battle it. Your body creates protective antibodies in response to the antigens the virus carries.
The traditional way to make a vaccine is to introduce dead or weakened virus into the body allowing the development of antibodies without making you sick. This is the way we’ve been making vaccines for over 100 years and it’s proven effective. However, it takes a lot of time and effort to make killed or weakened virus and a lot of testing has to be done to ensure the weakened virus doesn’t cause illness.
Many vaccines use this traditional method including the vaccines against Polio, Measles, Mumps, Smallpox, Hepititus A, Rabies and the Flu.
There are a few types of newer vaccine technology that use various delivery mechanisms to introduce parts of the virus into our cells to produce an immune response without using dead or weakened target virus. The key challenge for these vaccines is getting our cells to accept the introduced genetic material. There must be a delivery mechanism that can get inside our cells in order for an immune response to be triggered. Each of the below types of vaccines uses parts of the SARS-CoV-2 virus paired with a delivery mechanism that is not the SARS-CoV-2 virus.
Viral Vector Vaccines: These vaccines use an unrelated live virus that has been genetically modified to have SARS-CoV-2 antigens. The virus used as a delivery mechanism, called a viral vector, is one that does not cause illness but is effective in infecting human cells. Our bodies view these viruses as invaders and create antibodies in response. But, because the antigens carried by the virus are SARS-CoV-2 antigens, the antibodies our bodies produce will be protective against the SARS-CoV-2 virus. Two Ebola vaccines were created using this technology.
Nucleic Acid Vaccines: These vaccines work on the same principle as viral vector vaccines but use a different delivery mechanism. These vaccines use a strand of the virus’s DNA or RNA to create an immune response and are delivered along with short pulses of electrical current to cause temporary pores in cell membranes that allow the genetic material from the virus to enter our cells (think about that for a minute – crazy!).
This technology is very promising as it is easier to manufacture large quantities of this type of vaccine than traditional vaccines and creates a strong immune response. Notably, the Moderna vaccine that is in human trials and has been in the news recently is a Nucleic Acid Vaccine. This is a new technology and no Nucleic Acid vaccines have been approved for use.
Read more about Viral Vector Vaccines and Nucleic Acid Vaccines here.
Protein-Based (or Subunit) Vaccines: Compared to the prior two types of vaccines, these vaccines are relatively simple. They introduce a bit of the virus’s surface protein into our bodies. These proteins are non-infective (they can’t make us sick) but still cause our bodies to generate an immune response. A drawback to these vaccines is that like traditional vaccines they are difficult to make because the proteins have to be produced by altering bacteria or yeast or by purifying a viral toxin. More on Protein-Based Vaccines here.
This is how the vaccines are made for Hepititus B, Cholera, Tetnus and Diptheria.
A few important points:
- Technology is amazing! Think about the technology involved in these new types of vaccines!
- These new technologies don’t actually use SARS-CoV-2 virus, thus rendering the chances of getting the disease from vaccine at zero.