By Madeline Keleher
Feb 17, 2021
If you’ve worried about the safety of the new messenger RNA (mRNA) vaccines that protect against Covid-19, you’re in good company. In September, only 51% of Americans said they would probably or definitely get the vaccine (although that rose to 60% in December). Many of my friends with MDs and PhDs also worried at first. These are the very first mRNA vaccines to be tested in large-scale human trials; it is normal and healthy to be wary of the unknown. It is also important to learn what the science says, as science makes the unknown known.
Is the vaccine safe?
Yes, yes, yes! The vaccine is incredibly safe. Not a single person who received the Pfizer or Moderna vaccine died from the vaccine or from Covid-19. Not a single person was even hospitalized for Covid-19. That goes for the other five vaccines that have finished efficacy trials. Meanwhile, Covid-19 has killed 1.8% of those infected in the United States, including one of my friends who was just 35. The vaccines are safe and work remarkably well against a deadly disease that has claimed over 2.4 million lives.
The vaccine itself is just mRNA wrapped in a little fatty coat, both of which degrade within hours of entering your body. It’s actually a pain to work with mRNA in the lab because it degrades so quickly (to collect mRNA from mice for my dissertation research, I had to dissect each mouse at warp speed, drop its organs immediately into liquid nitrogen, and then store them at -122°F (-80°C) to prevent the mRNA from degrading). mRNA vaccines, though brand new, have several safety advantages over conventional vaccines. They are not made of DNA, so they can’t accidently insert themselves into yours. They also don’t have to be grown in chicken eggs (like the flu vaccine) or cells in the lab (like the chickenpox vaccine), so you don’t have to worry about biological contamination when creating them—this also allows mRNA vaccines to be produced much faster. So, these should be among the safest vaccines you’ve ever received.
Is the vaccine only safe for white people?
Distrust of the vaccine is particularly strong in communities mistreated by science and medicine. This is hardly surprising in a modern or historical context. Thousands of Black, Puerto Rican, and Native American women were sterilized in the 1970s without consent. Modern medicine was built on the cells of Henrietta Lacks, given to researchers by her doctors without her consent and still sold to this day. Tuskegee scientists recruited hundreds of impoverished black men for an experiment, promising them free government healthcare—instead, scientists neglected to inform them they had syphilis, withheld penicillin for more than 20 years, and convinced local doctors not to treat them (128 of the men died of syphilis or its complications and dozens unknowingly infected their wives and babies through pregnancy). To this day, people of color are underrepresented in clinical trials, minorities receive poorer quality healthcare and less information at medical visits, Black mothers die in childbirth at three times the rate of white mothers, and Black infants die at three times the rate if cared for by a white doctor than a Black doctor.
People of color have good reason to be skeptical of the healthcare system. However, it is important to note that when it comes to the Covid-19 vaccines, the clinical trials have included not only white patients, but also patients of color. Dr. Dakotah Lane of the Lummi Nation is recruiting people from his tribe for the Novavax trial to ensure it is inclusive of Native Americans. Moderna prioritized minorities in their clinical trial recruitment, even slowing down enrollment to find more people of color. They did not achieve perfect representation; however, it was superior to most clinical trials. The racial make-up of Americans aged 16 or older, compared to the racial make-up of participants in the trials, is as follows: 17.6% of people in the United States are Hispanic (as were 26% of Pfizer’s participants, 20% of Moderna’s), 0.8% are Native American (0.6% Pfizer, 0.8% Moderna), 0.2% are Pacific Islander (0.2% Pfizer, 0.2% Moderna), 5.9% are Asian (4.4% Pfizer, 4.7% Moderna), and 12.3% are Black (9.8% Pfizer, 9.7% Moderna). The efficacy of the Moderna vaccine is 94.1%; if you break it down by race, its efficacy is 93.2% in whites and 97.5% in people of color for preventing symptomatic Covid-19. Similarly, the Pfizer vaccine has 95.0% efficacy overall, with 94.4% efficacy in Hispanics and 100% in Blacks. The vaccines are definitely safe and effective for people of color.
Was the vaccine rushed?
Although it was developed faster than any vaccine in history, the speed was achieved not by cutting corners, but by generous funding, research pre-dating the pandemic, overlapping clinical trial phases, and companies manufacturing the vaccines early just in case they worked. You may be surprised to learn that developing vaccines has actually not been very profitable for pharmaceutical companies, so the billions of dollars of private and government funds that were poured into Covid-19 vaccine development were crucial to the speed. Furthermore, the mRNA vaccine was ready to be developed because of decades of government-funded basic science research on 3D protein modeling, modifying mRNA, lipid nanoparticles, and designing vaccines targeting the spike protein of other coronaviruses (SARS and MERS).
No steps were skipped in the development of the Covid-19 vaccines, but some were overlapped. Following pre-clinical trials in animals, clinical trials always proceed in three phases: Phase 1 (20-100 volunteers are tested for safety and dosage), Phase 2 (100-300 volunteers are tested for efficacy and side effects), and Phase 3 (300-3,000 volunteers are tested for efficacy and adverse reactions). The Covid-19 vaccines made it through trials and to production faster than usual because: the phases took place concurrently rather than sequentially; public interest was fierce so finding volunteers to participate wasn’t exactly difficult; and, even though less than one-third of Phase 3 trials are successful, Moderna started manufacturing its vaccine before the trials were done so they’d be ready in case their vaccine proved successful. No one skimped on the trials themselves. Phase 3 trials tend to be larger for vaccines than for drugs, with an average of 29,844 participants. Moderna’s trial enrolled 30,420 people and Pfizer’s enrolled 43,548. The vaccine development was not sloppy, but extraordinary.
Can I get Covid-19 from the vaccine?
No, you cannot. The vaccine does not include the coronavirus, just mRNA coding for its spike protein. The coronavirus uses the spike to get into your cells and make thousands of virus copies. The spike itself can’t infect you. Most people do have temporary side effects from the vaccine, such as pain at the injection site, fatigue, and headache, which are risks that accompany any vaccine. More people get these side effects with the new mRNA vaccines than with the flu shot, as the latter produces a weaker immune response (flu vaccines are only 40-60% effective). The flu vaccine triggers an allergic anaphylactic response in 1 in 1 million people, whereas Moderna does in 3 per million and Pfizer does in 5 per million (over 80% of whom had had previous allergic reactions). Anaphylaxis is a dangerous but treatable reaction and everyone has fully recovered—which is obviously not the case for infection with Covid-19, which has killed over 485,000 people in the United States alone.
Feeling under the weather for a day or two after receiving a vaccine is a sign that it’s working. Your immune system defends your body against an invader similarly to how you might defend your home against one. To start with, your innate immune system kicks into gear with a generalized, blunt response (such as inflammation)—much like how if you heard something go bump in the night, you might shout out “who’s there?” or “Fido, attack!” Being a vertebrate, you also have an adaptive immune system, which is more specialized and can remember invaders. With trillions of white blood cells, the cell mass of your immune system adds up to about the mass of your brain. White blood cells figure out the identity of the invader and devise a specially tailored way to destroy it. Similarly, once you’ve figured out what is invading your home, you’ll concoct an appropriate way to neutralize it: perhaps a mousetrap if it’s a mouse, capsaicin if it’s a squirrel, or a call to animal control if it’s a raccoon.
Vaccines are a way of teaching your body how to fight a specific pathogen without developing the actual disease. Let’s keep going with the home invasion analogy, and say the invader is a mouse. Vaccines activate your immune system in different ways. Some vaccines contain the pathogen itself, either dead—as in polio and flu vaccines (like you finding a dead mouse in your house)—or severely weakened like the MMR and chickenpox vaccines (like a neutered mouse, unable to fill your house with hundreds of baby mice). Other vaccines contain DNA with instructions for how to make a piece of the pathogen (like a book of instructions for how to build a mouse tail).
With the mRNA vaccines, instead of getting a dead or neutered mouse or a book that might sit on your bookshelf forever, you’re getting a set of self-destructing Ikea instructions for building a mouse head. Before the instructions burst into flame, you use them to build a bunch of model mouse heads (as your muscle cells build the spike protein), and then try out different ways to kill the mouse (as your body makes antibodies). Upon finding that a mousetrap suffices (like the right antibody that latches onto the spike protein), you store that in a drawer and in your memory. If a real mouse ever invades (or if you get infected with the coronavirus), you know exactly how to fight it. Ninety-five percent of people who are vaccinated don’t get any Covid-19 symptoms at all, and the 5% who do develop symptoms avoid severe cases (they don’t have to be hospitalized, and they don’t die).
Anyone else in favor of free mousetraps all around?
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