COVID-19 vaccine information and safety data

OVID-19 vaccines have finally started arriving in Colorado.  I know many of you have questions about their safety, the process they will be rolled out, and how to get a vaccine.  I'll try to provide those answers here with the info that is known at this time.

How does the COVID-19 vaccine work?

If you don't want a biology lesson, click here to skip to safety info.

The COVID-19 vaccine is an mRNA vaccine. To best understand how it works, you'll need a bit of background knowledge about vaccines and immunity, as well as DNA, RNA, and protein synthesis in our cells.

DNA, which is stored in the nucleus of our cells, is where our genetic code is stored.  Every gene encodes for a protein, and this is the way our genetic code is expressed in our bodies.  So for example, your eye color is determined by a number of genes, which encode for proteins that ultimately determine how much melanin is expressed in your eyes.  This is a simplistic explanation for a very complex process, but it gets the point across.

mRNA is the intermediary between DNA and proteins.  DNA is read in the nucleus of your cells and a strand of mRNA is created that corresponds to a section of your DNA.  The mRNA leaves the nucleus of the cells and travels to the ribosomes where the mRNA is read and a protein molecule is produced.  Through another complex set of processes, that protein then goes off to perform it's function in the body.

Switching gears to vaccines and immunity, at a very basic level a vaccine introduces a foreign pathogen (virus, bacteria, etc) into the body.  The body recognizes parts of it as foreign and develops an immune response through antibodies, cellular immunity, etc.  There are textbooks on this process alone, so I won't go into tremendous depth on it here.

The COVID-19 mRNA vaccine introduces an mRNA molecule into the body.  It is contained within a capsule of fatty molecules which delivers it into the cells.  Once in your cell, the ribosomes read the mRNA and produce the protein encoded in that mRNA.  In the case of the COVID-19 vaccine, it is the spike protein you have probably heard about that the virus uses to enter your body's cells.  Once the spike protein is produced, it is presented to the immune system on the surface of those cells, and your body will create an immune response to the spike protein.

To be properly immunized, you will need two vaccines 3-4 weeks apart.  Once your body has developed it's immune response to the COVID-19 spike protein, if you get infected by COVID-19 your body should rapidly attack and eliminate the virus before it can replicate and cause damage.

This CDC article covers this topic well.

Is the vaccine safe?

The evidence is strong for the safety of these vaccines.  From a biological theory standpoint, there are no glaring issues in the science of COVID-19 mRNA vaccines.  But data is what we really look at to see how the vaccine did in the real world.

For sake of brevity, I'll go over some data presented to the FDA for Pfizer's vaccine.  In evaluating safety data, the FDA compares data from the vaccine group to a placebo group (who received an injection that did not contain the COVID vaccine).  The reason it is important to compare to placebo is that if you were to evaluate 50,000 random people who did not receive a vaccine about any unusual symptoms over a period of 2 months you will naturally have people who had a fever, diarrhea, a hospitalization, or even died.  So for example, during the study 2 people who received the vaccine died, but 4 people who received the placebo died.  From this we can infer that the vaccine did not cause an increase in death rate.

Immediate and Injection Site Reactions

There were 43.448 participants in this study, half getting the vaccine, half placebo.  From this chart you can see that there was very little difference in immediate adverse events (think allergic reactions) between placebo and vaccine group.

There was a large difference in injection site reactions between these groups, but pain at the injection site was the most common reported reaction.  Severe pain, redness, or swelling was experienced by

Non-Serious Adverse Events

Systemic (or body wide) adverse events were also reported more frequently in the vaccine group (and more commonly after the second vaccine).  These effects were:

• Fever (
• Fatigue (
• Headache (
• Chills (
• Vomiting (
• Diarrhea (
• Muscle pain (< 37.3% vs
• Joint pain (

So basically the normal side effects you would expect from getting a vaccine.

Serious Adverse Events

As for serious adverse events, there was a very slight increase in these for the vaccine group compared to placebo, a difference of about 0.1%.  So essentially 1 in 1000 people had a serious adverse event from the vaccine, but most of the serious events were enlarged lymph nodes. Here are the significant reported serious adverse events that were possibly related to vaccination:

• Lymphadenopathy (enlarged lymph nodes) - 64 in vaccine group (0.3%) vs 6 in placebo group
• Bell's palsy - 4 in vaccine group (< 0.01%), 0 in placebo - investigators commented that the 4 in the vaccine group were in line with the expected frequency of Bell's palsy in the general population, but couldn't rule out that this adverse effect was related to vaccination.

There were other adverse events reported but which occurred at such a low frequency (typically 1 or 2 people) and with no major differences between the vaccine and placebo groups that the investigators concluded they were not related to vaccination.

Long Term Side Effects

One common critique is that there was not a lot of time to study these vaccines, and this is true.  However, the overwhelming majority of vaccine side effects occur within a 2 month period and would have been captured in these studies.  Side effects that occur months to years after a vaccine are exceedingly rare, and while there are no guarantees with anything in life, medical experts agree long term side effects are not a cause for concern.

Ultimately, experts in the fields of virology, immunology, population health, etc overwhelmingly agree this is a safe vaccine.  I know some of these people, have heard some of them talk about the vaccine, and I know how respected they are within the medical field.  Their vote of confidence in combination with the data above leads me to feel confident with this vaccine.

Will you be getting a vaccine?

Absolutely.  The safety and efficacy data is overwhelmingly positive, and the short and long term effects of COVID-19 infection can be downright scary.  I am high risk for exposure to COVID-19 because of my profession, but I am low risk health-wise, however the incidence of COVID-19 related cardiomyopathy, thromboembolism, new mental health diagnoses, auto-immunity, and long term lung damage (to name a few) is cause for concern for even a healthy person.  When comparing the risks of vaccination vs the risk of COVID-19 induced disease, the vaccine is exponentially safer.

Where can I get a vaccine?

This question is a bit trickier.  In Colorado vaccines will be given in a phased rollout based on risk.

Phase 1 focuses on healthcare workers, long-term care residents, and other front-line workers with high risk of exposure. The initial shipment of vaccines for Phase 1A have gone to large hospital systems who are currently focusing on vaccinating their staff.  As far as we know right now, public health departments are responsible for everyone outside those hospital systems, but Jeffco Public Health is only slated to receive 200 vaccines at this time.  Healthcare providers in Phase 1B are being told it may be a couple months before they can be vaccinated. Older and higher risk individuals in the general population fall into Phase 2 which will be this Spring, and everyone else is Phase 3 which is summer. Check out the infographic from CDPHE:

So how do you get a vaccine when the time comes? Unfortunately there is not a great deal of info at this time.  At Pure Family Medicine, we have applied to receive vaccines for our patients, but we likely won't know anything further until we get closer to Phase 2.  As the vaccine rollout expands, I am being told that the health departments will be using local pharmacies and community health centers to help vaccinate the public.

So for right now, if you are in Phase 1A or 1B, contacting your employer or public health department is your best bet.  If you are in Phase 2, stay tuned, but don't expect a vaccine to be available until Spring at the earliest.

Should I get the vaccine if I already had COVID-19?

Consult with your doctor, medical experts are advising that yes, people who have had COVID-19 should still get the vaccine. Evidence is showing that immunity from natural infection only lasts for a few months, whereas it is suspected that immunity from the vaccine will last much longer.

Will I need to get vaccinated again in the future?

Probably, but we just don't know how long vaccine induced immunity will last. Many experts predict at least a few years of immunity so the need for a yearly COVID vaccine like we do with influenza is not expected.

Will the vaccine stop the COVID-19 pandemic?

Yes, while it is very unlikely that COVID-19 will be completely eradicated, the vaccine is supposed to put an end to the pandemic. With 95% effectiveness, experts predict that between 75%-85% of Americans would need to be vaccinated to achieve the elusive "herd immunity" that will stop widespread infections. Current opinion polls show that 84% of Americans plan to get the vaccine. That is very encouraging, and it definitely feels like there is a light at the end of the tunnel.