COVID-19 Vaccines: What You Need to Know Now

Aaron S. Weinberg MD, MPhil
January 22, 2021
9 Min

This month saw the release of two new vaccines designed to combat COVID-19, with plans for more pandemic-fighting vaccines to roll out in the months ahead. While people are both excited and nervous about what the future holds, there are, understandably, many questions surrounding the vaccines. What are the similarities and differences between the two vaccines? How do they work? How effective are they? What are the side effects? When do I get my shot? We aim to address some of the more pressing issues now.

COVID-19 Vaccines: A New Medical Frontier

As deaths from COVID-19 surge, the FDA recently approved emergency use of Pfizer-BioNTech’s and Moderna’s vaccines for COVID-19, and there are several more types of vaccines to fight the pandemic in the works.

The Pfizer-BioNTech and Moderna vaccines are similar in many ways. Both are administered intramuscularly, both require two shots, and both yield close to 95% effectiveness in preventing a COVID-19 infection in clinical trials. In addition to preventing any illness, those who were vaccinated and still became infected were less likely to develop a severe form of COVID-19.

However, there are key differences. Pfizer’s vaccine is recommended for people ages 16 and up, while Moderna’s vaccine is recommended for ages 18 and older. The second shot of the Pfizer vaccine should be taken 21 days after the first, while the second Moderna shot should be taken 28 days after the first shot. Pfizer’s vaccine needs to be stored at the super-cold temperature of minus 70 degrees C, whereas Moderna’s vaccine can be stored in a home freezer.

How mRNA Vaccines Differ From Traditional Vaccines

One major similarity of the Pfizer-BioNTech and Moderna vaccines: Both are mRNA vaccines, or nucleic-acid based technology that has been studied for decades.

Unlike traditional vaccines, a mRNA vaccine does not include dead or modified live viral elements. Instead, it contains a code for a vital protein located on the virus, in this case the COVID-19 spike protein. The mRNA vaccine acts as a messenger or recipe card that enters our cells. Our cells then “read” the message, create the encoded protein and display it on the outer cellular membrane. The immune system recognizes the protein as foreign and creates antibodies against it. If exposed to COVID-19 in the future, vaccine recipients will then have antibodies and specially trained T-cells to protect them.

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The mRNA vaccine is also shown to produce a strong T cell response, giving it a distinct immunological advantage. Both a strong antibody and T cell response is needed for a COVID-19 vaccine to be effective. After delivery of the coded message, the mRNA is quickly and safely degraded by the body. It cannot change our genetics, because it never enters the cell nucleus, the storage house for our genetic code. It only enters the cytoplasm, the thick solution that fills each cell.

Both vaccines need to be kept frozen and will be delivered from labs to clinics all over the country using “the cold chain” method. The Pfizer vaccine is manufactured in Michigan, put in vials and shipped in large thermal containers packed with dry ice to hospitals and clinics. It will be shipped at -70 degrees C. Moderna’s vaccines are being manufactured in Pennsylvania, New Hampshire, and Indiana and shipped in containers at -20 degrees C to the main center for the Federal Government’s Operation Warp Speed, located in Irving, Texas. From there, it will be shipped in freezers to clinics around the country. All shipments will be monitored with temperature probes to make sure the vaccines don’t spoil.

Two Shots Are Better Than One

Each vaccine requires two shots, and it’s important to get both for maximum effectiveness. After receiving the first shot there is a three week wait time for the second shot while the body primes the immune system. We won’t know how effective the vaccine is if you receive the second dose more than 23 days after your first dose. This wasn’t specifically studied in clinical trials and the concern is the vaccine may not be as effective as taking it within 19–23 days after the first dose.

The first shot of the mRNA vaccine can help reduce the chance of getting symptomatic COVID-19 by 52%. It is 95% effective one week after receiving the second injection of the vaccine.

Also, it is crucial to stick with the same vaccine brand. Your second dose of vaccine must be manufactured by the same company that made the first dose of your vaccine. For example, if your first shot was the Pfizer vaccine, stick to that for your second shot. Then vaccination may not work properly if you get two separate types of vaccines. When you are vaccinated the first time, you will receive a vaccine card and/or be enrolled in an electronic system so you can keep track of the date, type, and specific batch of vaccine you received. If you miss your second dose, your chances of being protected from the virus go down significantly.

The CDC has yet to release recommendations for booster shots but will do so in the near future. Boosters may be important because, as with influenza and other viruses, COVID-19 mutates in an attempt to escape the immune system. Vaccines will need to be updated to match these mutations. The good thing about m-RNA vaccines is that they can be easily tweaked to match the new mutations.

The Vaccine is Safe, Right? Fact vs. Fiction

Some people are concerned about the safety of the vaccines because of how quickly they were developed. Historically it takes 10–15 years to develop and test a single vaccine and the COVID-19 vaccines came out within months. While scientists and experts accelerated the process because of the pandemic and the ability to easily enroll study subjects due to the prevalence of the condition, no developmental steps were skipped, and safety was critically evaluated. In fact, clinical trials have important third party committees built into the process which monitor the data and any safety issues that arise and these groups are free of any political or economic bias or gain.

Also, scientists have been working on an mRNA vaccine for nearly 30 years and were able to build on the current evidence base rather than start from scratch. The safety profile of the mRNA vaccines is similar to FDA-approved vaccines, with the most common issues being temporary injection site pain, fatigue, and headache. Bell’s Palsy, or temporary weakness and one-sided facial paralysis, has been reported in participants in both the Pfizer and Moderna trials. The CDC is actively monitoring this, but does not think it was caused by the vaccine as the incidence of these findings in the study population was the same as what we typically encounter in the general population. In fact, Bell’s Palsy mostly occurs after a viral illness and has been associated with COVID-19 infections, not the actual vaccine.

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The side effects from both COVID-19 vaccines are normal and consistent with other regularly-used, FDA-approved vaccines. A common side effect of the first shot is local injection site soreness of the muscle. With the second dose, about 20% of patients may develop side effects like body aches, chills, and feverishness which typically last a day or less and are treated with acetaminophen or ibuprofen. These are all completely normal and expected and indicate that the immune system is responding appropriately. That’s a good thing!

Authorities are monitoring a severe (but rare) anaphylaxis or allergic reaction to the vaccine. Patients who have a history of anaphylaxis to a component of the vaccine, other vaccines or medications are being cautioned. Everyone is being monitored after injections for a short period of time for signs and symptoms of this.

infographic describing the vaccine distribution from first in line to last in line

Who Gets the Vaccine First?

Vaccine supply will be limited in the early days of distribution, and effectiveness will be continually monitored and updated.

Here’s the expected order for vaccination distribution in the United States according to the CDC guidelines:

Healthcare workers and people in long-term care facilities: Starting in December, the vaccine will start to be rolled out to healthcare workers and elderly people living in long-term care facilities. Initially, there won’t be enough doses to vaccinate all healthcare workers, so states will prioritize based on exposure risk, choosing emergency room staff, for instance, to go first. Or they may offer the vaccine to the oldest healthcare workers first.

Essential workers: The 87 million Americans who are firefighters, police officers, corrections officers, food and agricultural workers, United States Postal Service workers, manufacturing workers, grocery store workers, public transit workers, and those who work in the educational sector (teachers, support staff, and daycare workers) and other frontline essential sectors will likely be second in line, starting early 2021. Individual states will set priorities. Arkansas, for example, has proposed including workers in its large poultry industry, while Colorado wants to include ski industry workers who live in congregate housing.

Adults with underlying medical conditions and people over 75: Health officials are hoping to get any remaining older adults who have not been vaccinated sometime in the first quarter.

All other adults: Adults in the general population could start receiving the vaccine as early as April although many people likely will have to wait until at least May or June. The vaccine hasn’t been approved in children, so it may be several months, or possibly a year, before the vaccine is available for anyone under the age of 16.

If you have already recovered from COVID-19, you can still get vaccinated once your active COVID symptoms have subsided and you are removed from quarantine. Experts are unsure how long natural immunity lasts. For people who received passive antibody therapy, the recommendation is to wait 90 days after onset of infection to get vaccinated. Currently, the CDC recommends that people who’ve had a severe allergic reaction to any component of the Pfizer vaccine to not get vaccinated. You can access a list of those ingredients here. Anyone who has had a severe allergic reaction to other vaccines or medical therapies should discuss the risks and benefits with their clinician. While a safety and effectiveness profile for immunocompromised people and those who are pregnant or breastfeeding has not yet been fully studied or established, they can still get the vaccine but should discuss the risks and benefits with their doctor(s) first.

Why Vaccines Are Crucial

It’s important everyone who is eligible to receive the vaccine gets it. Not only will it help protect you from getting COVID-19,but it will also help build herd immunity in your community. Herd immunity is reached when enough of the population is immune to COVID-19 and the spread significantly slows down. Because COVID-19 is such a new virus, experts do not know the exact number of people who will need to be vaccinated to achieve herd immunity.

Returning to Our Pre-Pandemic Lives

Public health officials and doctors are constantly gathering new information about the virus and updating guidelines. The CDC is calling for those who are immunized to continue wearing masks and practicing safe physical distancing until more is learned. While that might seem confusing and frustrating to some, experts need to evaluate the effectiveness of the vaccine in slowing the spread of COVID-19 before lifting the mask recommendation. Until we have that information, we need to continue to utilize all resources available to slow the spread and conserve our healthcare capacity.

The COVID-19 vaccines are our most promising tools when it comes to beating the virus and returning to our pre-pandemic lives.

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Aaron S. Weinberg MD, MPhil

Aaron S. Weinberg, MD, MPhil, is Director of Program Development at Carbon Health and triple board-certified in Pulmonary, Critical Care, and Internal Medicine.


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