A lot of my patients and friends have been asking me questions about COVID-19 vaccines. I’m sure many of you have read or seen information about the vaccines in the news, but I’ll start from scratch for those who have not. This is a huge topic and rather than try to squeeze some basic information into one column, I’ve chosen to go into more detail and split up my treatise over three weeks.
The number one question I get is when and where someone can get a COVID-19 vaccine. Some think vaccine is already available and want to schedule a time to get it. People are also concerned about the safety of the vaccines. Before I get to safety and distribution I want to review the basics of the first three vaccines that are likely to be approved soon by the FDA and how they work.
Our immune system is designed to recognize foreign organisms or substances and rid our bodies of them. This is accomplished in two ways: (1) by producing antibodies to bind to and neutralize the invader and, (2) training specialized immune cells to recognize, kill, and remove cells that have been infected. Vaccines work by introducing non-infectious substances into the body that fool the immune system into thinking an infection is taking place so that when a real infection occurs, the immune system is already primed to fight off the invader.
SARS-CoV-2, the coronavirus that causes COVID-19, binds with the cells in our body through an interaction with the “spike protein,” the protrusions everyone has seen on the outside of the virus that gives the virus its corona or crown-like appearance. The spike protein has been the focus of vaccination research and development.
When the spike protein of SARS-CoV-2 binds to our cells, the virus releases its genetic material (RNA) into our cells where it hijacks our cellular machinery to make virus proteins including the spike protein. These parts are then assembled into the full virus and released from our cells to cause more damage or to be expelled from our bodies to infect other people.
Vaccines have traditionally contained single or multiple proteins derived from infectious microorganisms, sometimes mixed with other materials called adjuvants that improve the immune response. While there are many different types of COVID-19 vaccines in development, three are leading the pack. Two of the three utilize a new methodology to produce an immune reaction.
These two vaccines were developed by Pfizer/BioNTech and moderna. Instead of injecting foreign proteins into the body, these vaccines will contain a snippet of the SARS-CoV-2 genetic material (messenger RNA or mRNA) packaged inside of microscopic fatty bubbles. This mRNA will cause our cells to crank out loads of spike protein but not the other 24 parts of the virus that allow it to assemble into a fully infectious virus. Fun fact – the name moderna is derived from the way the vaccine works: “mode” plus “RNA.”
The Pfizer/BioNTech vaccine will be given in two doses, 21 days apart. Current data from phase three clinical trials indicate this vaccine is 95% effective in preventing mild and serious cases of COVID-19. It is also 94% effective in those over 65 years old. The moderna vaccine is given in two doses, 28 days apart and has been shown to be 94.5% effective.
The third vaccine that will likely soon be approved was developed by AstraZeneca and the University of Oxford and introduces the spike protein into the body via a weakened chimpanzee virus “vector.” This chimp adenovirus acts like a Trojan Horse to deliver the spike protein, but does not cause disease in humans. The efficacy of this vaccine has been shown to be 62% in one arm of the phase three trial and 90% in another depending on the dose given. It was also effective in older age groups.
Some people fear that the SARS-CoV-2 genetic material in the vaccines will mix with our own DNA but it doesn’t work that way. The viral genetic material in the vaccines is temporary, like Post-It notes that are read and thrown away. It also can’t combine with DNA.
There are many more vaccines in development and if things go according to schedule, we will likely be able to get everyone vaccinated sometime in 2021 (more on that in a future column). One question that has yet to be answered is if the vaccines will prevent someone who is vaccinated and then infected by the virus from transmitting it to an un-immunized person. We still have things to learn.