With the recent emergency use approval of two independent vaccines for SARS2-CoV-2, the virus responsible for the horror that is Covid-19, many folks have questions: What the heck are these vaccines? Are they safe and effective? Should I get one?
Note: I’m not going to dignify any wild conspiracy theories about vaccines and microchips. Bill Gates doesn’t care about you or me or anyone else he doesn’t know and he has better things to do that track you with a microchip in a vaccine. Seriously. People believe some weird shit… If anyone wanted to track you, they’d do it digitally by your freakin’ cell phone.
Also, vaccines don’t cause autism. Period. They. Fucking. Don’t.
That being said, the first three questions are completely legit. My goal in this post is to break down the science behind the Pfizer and Moderna vaccines, what we know so far about their safety and effectiveness, and dispel some common misconceptions about them.
First, here’s a crash course on how your immune system fights infections. This is important, since vaccines harness the power of your immune system to mount a rapid and robust defense if and when you encounter the actual pathogen (i.e. virus or bacteria that cause disease) in your daily life. The arm of the immune system that does this is called the adaptive immune system. The other arm is the innate immune system and includes natural barriers like skin, the tiny hairs and mucous in your nose, and stomach acid.
How does the adaptive immune system work? First, it involves cells that roam around your body looking for something suspicious. Cells like macrophages and dendritic cells, which patrol various organs and tissues, find pathogens like bacteria or unhealthy cells infected by viruses like SARS-CoV-2, and eat them (fancy word is phagocytosis). Infected or damaged cells send out protein signals called cytokines as a distress call to attract macrophages and dendritic cells. While “digesting” the bacteria/infected cell, they salvage proteins or pieces of proteins—antigens—that identify the bacteria or virus as “other,” and they present these to immune cells, usually in lymph nodes, that mount an immune response. Macrophages and dendritic cells are known as professional antigen presenting cells (APCs)
When activated by APCs, immune cells called B-cells produce antibodies against the antigen, which can do a lot of things to fight an infection. Some antibodies neutralize the pathogen by binding it and stopping it from entering a cell. Other tag infected cells for other immune cells to come and kill them. Others coat pathogens or infected cells in a process called opsonization (meaning to “make tasty”), which signals other cells like macrophages to come and eat the coated pathogens/cells. Specialized B-cells called memory B-cells archive the information about the antigen so your immune system can recognize the pathogen when it hits you again and mount a faster immune response.
Other immune cells called T-cells become activated by APCs and mount a different kind of immune response. Cytotoxic T-cells seek out and kill infected or damaged cells, and helper T-cells help activate B-cells so they make antibodies, activate cytotoxic T-cells, and activate macrophages to go eat nasty invaders and infected cells. Memory T-cells also archive information about past infections to mount a rapid, strong response the next time your body sees it.
That’s a simplified by hopefully digestible explanation of immunity and the major players (there are other immune cells, but APCs, B-cells, and T-cells are the biggies). Memory is key to protection, and memory is built by exposure to pathogens.
But what if there was a way to expose your body to pathogens without making you sick? That’s where vaccines come in!
The way vaccines work is to tap into this process and activate the adaptive immune response using an artificial antigen supplied by the vaccine, getting your immune response geared up and, importantly, building those archival memory B- and T-cells that will recognize the real infection when your body encounters it so it can rapidly fight it. Types of vaccines include: Live-attenuated vaccines; Inactivated vaccines; Subunit, recombinant, polysaccharide, and conjugate vaccines; Toxoid vaccines.
Live-attenuated means using a weakened form of the virus to initiate an immune response—examples include measles, mumps, and rubella (MMR) and chickenpox vaccines. Inactivated means using a dead version of the virus that cannot infect cells but contains antigens that can be used to activate adaptive immunity—examples include flu, hepatitis A, and rabies vaccines. Subunit, recombinant, polysaccharide, and conjugate vaccines use pieces of the virus that act as antigens, like proteins and sugars—examples include HPV, hepatitis B, and shingles vaccines. Toxoid vaccines use toxins produced by the pathogen to mount an immune response against the toxic protein—examples include tetanus and diphtheria vaccines.
What the heck are these (Covid-19) vaccines?
The current FDA approved (for emergency use) Covid vaccines from Pfizer and Moderna belong to a newer class called mRNA vaccines. See my previous post on DNA to mRNA to protein (Central Dogma of Molecular Biology) for a refresher on mRNA. This is really just a modification of the subunit, recombinant, polysaccharide conjugate vaccine approach in that it delivers messenger RNA coding for the SARS-CoV-2 spike protein, which the virus uses to enter a cell, instead of delivering the spike protein itself. See my previous post on SARS-CoV-2 for information about the spike protein. The cells in your body that take up the mRNA make spike proteins themselves, which in turn activates your immune system and provides protection.
Are they safe and effective?
Since these are new vaccines approved for emergency use, and since due to the accelerated nature of their development and approval, some people are understandably wary of their safety and ability to protect against Covid.
While they may be new, a lot of the groundwork for these vaccines started in in 2002 with the emergence of the first SARS virus (SARS-CoV) and continued with study of the related MERS-CoV virus. SARS-CoV uses the same spike protein to enter target cells through angiotensin-converting enzyme 2 (ACE2). Scientists learned a great deal about coronaviruses by studying SARS-CoV and MERS-CoV, including how to develop vaccines.
Let’s look at safety first. Clinical trials involving tens of thousands of healthy volunteers have been performed. Safety concerns include allergic reactions to the vaccine or components of the vaccine. Providers who deliver the vaccine are equipped to deal with anaphylaxis on site, which is why you’ll be asked to hang around for 15 minutes after your shot just in case. You might feel feverish, fatigued, and generally yucky the day after one or both shots (the first activates the immune system and the second gives it a signal boost), which is NOT a sign that you have Covid. It actually means your immune system is working, building memory and its arsenal of weapons to fight Covid if you encounter the real virus.
The FDA is continuing to monitor those who received the vaccines in clinical trials, as well as those who received the vaccines after emergency approval. So far, they appear to be safe.
As far as effectiveness, data from trials looking at the number of Covid-19 cases in trial participants relative to the total number of participants revealed that the Pfizer vaccine is 52% effective after the first shot (39 cases of covid-19 in the vaccine group and 82 cases in the placebo group) and 95% effective after the second shot (8 covid-19 cases in the vaccine group and 162 cases in the placebo group; 43,448 trial participants) – New England Journal of Medicine (NEJM). Similar efficacy was reported for the Moderna Vaccine in NEJM.
There’s still a lot we don’t know – most importantly, we don’t know how long immunity produced by these vaccines will last. Some experts hypothesize they might provide a year or two of immunity, after which you’ll need more shots, but we won’t know until we see in real time as we track vaccinated people.
Should you get the vaccine?
The more people who are vaccinated against this virus, the better. Vaccines will slow the spread of the virus by preventing infections in vaccinated people. Along with mask wearing and social distancing, the vaccines are a vital tool in stopping this pandemic. As a cancer survivor, I’m in a high risk category, meaning Covid-19 could kill or debilitate me. The same is true for people with diabetes and other underlying medical conditions.
That’s why I got my vaccine! Had the second shot a few days ago, which gives me peace of mind as I prepare to return to work after reconstruction surgery. I’m with Dr. Fauci on this one, and I encourage everyone to talk to their healthcare providers about getting vaccinated.
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