Covid-19 Vaccine Questions: Are mRNA Vaccines Safe? Will They Alter my DNA? How Do They Work?

There has been so much excitement in the news recently about the recently-approved mRNA-based vaccines. But there are also a lot of questions, like how do we know it’s safe? How exactly is mRNA different than a normal vaccine? Do you trust it enough to take it yourself? I can answer a lot of these questions as a scientist who does Immunology work and has a lot of clinical testing and regulatory experience.

What is mRNA?

DNA is made of two complementary strands (meaning that one strand is the opposite of the other, in the same way that a socket is the opposite of a plug and that’s how they fit together). Your DNA contains all of the code for your body and is kept in the nucleus (essentially the brain of the cell); in order to express this code it sheds messenger RNA (a single strand), which is then released into the cell and decoded by a ribosome (a molecule floating around your cell just for this purpose). When the ribosome sees the mRNA strand, it just fills in the gaps with the exact opposite, which makes a protein! And very quickly after, the mRNA is dissolved (it’s very unstable), and the protein exits the cell.

Will the mRNA vaccine alter my DNA?

The mRNA cannot re-combine with your DNA. This is not a perfect analogy because I’m not debating modern horticulture or whatever, but think of your DNA like an apple tree. The mRNA is like the apple that grows from the tree and falls off. Once that apple hits the ground, it has a short time before it rots. You can’t just take the apple and stick it back on the branch, it won’t connect properly ever again. In the same way, when mRNA leaves your DNA, it will not reconnect, it will just start to degrade. It’s only purpose is to hook up with a ribosome, make a protein, and dissolve into goo.

The mRNA vaccine works the same way, except instead of mRNA coming from your DNA, it comes from a lab. Once the mRNA is injected in your body, it is hopefully absorbed into a cell, where a ribosome reads it and makes the protein, in this case a “spike protein” which is part of the covid-19 virus.

In fact, when scientists were developing the mRNA vaccines, the problem was not whether it would alter a person’s DNA; rather it was, how do we make mRNA stable enough to even make it to a cell? Because like I said, it really wants to dissolve (actually it’s better to say that everything else just wants to digest it). And if the mRNA doesn’t make it to the cell, it can’t produce the protein, making it ineffective. So after much research, scientists discovered they could put it into a fatty shell (lipid), and that would protect it enough to get to the cell. In the same way that a candy wrapper protects the candy inside until it gets in your mouth.

How exactly do mRNA vaccines work and what’s with all the hype?

In short, mRNA vaccines have the potential to provide a more targeted response and they are easier to make.

Traditional vaccines work by injecting the patient with a weakened virus, and they work very well and we have a lot of data to back that up. However, making vaccines can be tricky; you need to grow the real virus (which is hazardous, takes time, and can be tricky), and each batch is slightly different, which makes manufacturing reliable doses difficult. However, the process used to make mRNA is relatively simple and we can grow large batches in the lab (not hazardous because there is no actual virus involved) much quicker. Also, once we know what protein we want to make, figuring out the mRNA is relatively easy.

Traditional vaccines mimic what happens when you get sick; an antigen gets into your body, your immune cells discover it and break it up into pieces (small proteins), and send it to your central immune system, where your body makes antibodies. These antibodies then flood your system and stick to the antigen, and then other white blood cells come along and kill anything with an antibody on it. By putting a weakened virus into your system, your body has the benefit of being able to fight it off, and also recognizing when the real virus gets in (and crushing it when it does).

The advantage to mRNA vaccines is that instead of putting a virus inside of you, the mRNA uses a biological process that your body already does (making proteins from RNA) to turn your cells into little vaccine factories, where they spit out pieces of the virus (proteins), which your white blood cells react to and form an immune response (in the same as with a real virus). And since we have more control over mRNA, we can encode it so that it makes proteins that span multiple strains of the same virus, which helps make us more resistant to viral mutations.

In fact, mRNA technology has been around for decades and has been used for cancer research. The vaccines were the next logical step and were already somewhat in development.

Are the vaccines safe? Would you take it?

As a scientist and a feminist, I believe that everyone should have enough information to feel empowered to make a reasonable choice. I also hope that by helping you to understand HOW mRNA works, you will feel more comfortable taking the vaccine.

In fact, it is OK to be skeptical of the vaccines! There are a lot of questions that people have that should be answered with more than just faith and trust. If you are uncertain, that is a completely valid feeling too.

I believe the mRNA vaccines that go through the approval process are safe. They have been through extensive safety testing and the data has been reviewed by multiple scientists and regulatory agencies (in fact, I have been through plenty of FDA audits so I can personally attest to how thorough they are!). The clinical trials have been shortened, but the actual amount of time it takes to collect data has been the same; there have been people working around the clock to process the required paperwork and also some parts of the clinical trials ran simultaneously. You don’t normally see a vaccine progress this quickly because there is not an incentive to do so (it costs a lot of money to run trial so quickly). But if any of the paperwork did not meet regulatory standards, the vaccines would not be approved. And in fact there are multiple vaccines that were not effective or had potential safety concerns that didn’t make it to Phase III trials, so we know the process is working as it should. And we are still going to collect long-term data in case there are rare side effects and to test the vaccine effectiveness.

If I had the option to take an approved vaccine, as of now, I would do it. And I hope that enough people feel the same that we can get some critical mass behind it and stamp out the virus for good. If you are unsure whether the vaccine is right for you (if you have a health condition or other concern), please make sure to talk to your doctor to get the right information.


Mary Brock works as an Immunology scientist by day and takes care of a pink-loving princess child by night. She likes cloudy days, crafting, cooking, and Fall weather in New England.

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  1. I’ve read that there’s another advantage to the mRNA vaccines: they only evoke an immune response to the specific proteins the vaccine makers chose. If you use the actual virus, some of the virus proteins might be similar enough to some of the patient’s proteins that the body’s immune response would also attack the body, creating an autoimmune disease. The vaccine makers can choose virus proteins that are unlikely to be similar to any (known) human proteins.

    I’m not an immunologist, but this explanation sounds plausible.

    1. Yes that is absolutely correct! By only coding for a small part of the virus, we can produce a more controlled result with fewer serious side effects like autoimmune disease. That’s why vaccines have to go through extensive safety testing before Phase III trials (and also to prove that they work and to get the dosage correct).

      Another advantage to the mRNA vaccine is that your body not only produces antibodies to the specific proteins, but also it causes a longer-lasting immune response by stimulating memory cells (that produce antibodies on demand and can potentially stay in your system for years).

  2. I still say I’m going to acquire mutant superpowers and I can’t wait.

    (Sorry Mary, I haven’t actually read the article yet, but the headline was just too tempting. I promise I will read it after dinner…)

  3. We in Australia are watching like hawks to see, among other things, how you in the US and UK solve the logistical problems in the rollout of a -70C vaccine. (We are scheduled to start in March).

    It seems there are problems in administration as opposed to delivery. One site monitoring this is here:!/vizhome/COVID-19VaccineAllocationDashboard/Dashboard1
    (Perhaps there is a better site?)

    It seems that after two weeks not even the first delivery has been administered, perhaps 2 million out of 20 million promised by Dec 31st.

    I have been wondering how the millions of old folks prioritised in the first phase are to be teleported from their beds in the nursing homes into the large hospitals where the vaccines are stored? Are they going to be bused in, maintaining adequate social distancing to prevent a super spreader event? Are they supposed to queue up outside all day in the snow?

    What I have actually seen in the press are pictures of medical staff of working age being vaccinated. Oh and politicians. It seems that to keep the daily numbers up the hospitals are vaccinating everybody in reach on the site.

    To add to this, in the UK at least, there was a problem with the impossibly large pack sizes, a pack of 5000 shots in 10 vials, one vial to be used within 3 days. Perhaps there are different and more appropriate pack sizes in the US?

    Even worse, it was forbidden to split the vials except at authorised centers. I have not seen any follow up about how this Catch-22 was overcome, do you have any information on that?

    Once again, I am concerned that to reduce mortality and empty the ICUs the older population must be vaccinated initially. To prioritise the working population, even medical staff, will not achieve very much at all.

      1. I’ve been reading a lot of unofficial accounts of how the roll-out in the US is going on Twitter and it seems like there is no clear strategy from the federal government (completely unsurprising for this administration but still disappointing). From what I’ve seen, the vials have been distributed to states and hospitals without a plan so everyone has to come up with their own. Which they’ve had months to do, but just for some reason haven’t done. I don’t work in that side of healthcare so I can’t speak to what’s going on behind the scenes but there are a lot of frustrated people for sure.

        1. Thanks for the reply, Mary!

          Worst fears confirmed by this thread re the situation on the ground in Florida right now.

          Crowds of seniorsin their 80s lining up for hours or even overnight in the cold, maskless. De Santis ignoring CDC guidelines – everybody gets only one shot. Snowbirds from out of state prioritised. Phone bookings systems absent or crashed.

          You would get better treatment in Malaysia or Indonesia and I speak from experience.

          1. I feel like the outgoing administration is just counting down the clock. They don’t want to help out the Biden administration at all, they want to set them up to look as bad as possible. They don’t even care about the people who have died, it’s just a pissing match to them. Unconscionable.

    Meanwhile Israel has vaccinated 10% of the population in only 2 weeks! ofc they have a universal health care system that is vertically well integrated, and therefore by definition they are a communist toilet and no model for the USA to follow.

    Interestingly the one shot vaccine protocol that De Santis is pushing seems to have some scientific basis (70-80% effective).

    I know that in desperation they are doing that in the UK also. Again, ironically, that was originally suggested by ex Labour leader Tony Blair, who would def be a communist and no example for the USA to follow. But, yeah, Republican talking points are neither consistent nor logical nor sane!

    1. Israel also has a much smaller population with a much higher density, which makes the logistics for mass vaccination much easier. Which isn’t to downplay their accomplishment, of course, just to say that Israel’s protocol probably wouldn’t have mapped to a 10% vaccination rate in the US in the same amount of time.

      But still, if we had what Israel has, we’d absolutely be way further along at this point.

      1. Makes me wonder what would happen if you took a small state like DE or RI and fully vaccinated there, which with some effort, could be done in about a week Then monitor the irl effects on cases, transmission, hospital admission, mortality etc. The results could be extremely valuable.

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