COVID-19 Vaccines: How They Work and Why You Should Get One

Since breaking news of the highly effective and newly available COVID-19 vaccines, there’s been palpable anticipation and hope in how I’ve heard people talk about the future. To date, over 100 million doses of COVID-19 vaccines have been administered in the United States. The results have been overwhelmingly positive and a world without COVID-19 restrictions and social distancing feels closer than it has in the past year.

Yet for each person ready for the vaccine and planning out a return to normalcy, there is another who might be deliberating over how it works and if they will choose to get vaccinated. Importantly, these futures are intertwined and we cannot have a future free of COVID-19 restrictions without widespread vaccination. So, here is what you need to know about the several COVID-19 vaccines currently available and what they mean for you, your friends, your family and our UC Santa Barbara community.

A vial containing the Pfizer-BioNTech COVID-19 vaccine. Courtesy of the Department of Defense

How do vaccines work? 

To start our conversation about vaccines, let’s first get on the same page — how does a viral vaccine work? First, vaccines take harmless parts or versions of a virus and allow our immune system to build up a defense against them before coming into contact with the actual dangerous, live virus. Vaccines like the annual flu vaccine, the chickenpox vaccine and the measles vaccine use dead (inactivated) or weakened (live-attenuated) versions of the virus. The dead or weakened virus is injected into your arm where your body’s white blood cells recognize the foreign antigens, build up a specialized defense based on the virus’s appearance and attack the virus. Importantly, your body stores this information in its memory immune cells so, if you were to encounter the live virus in the future, your body would quickly recognize and destroy the virus particles before it can make you sick. Thus, you are immune. From start to finish, a vaccine gives your body the opportunity to build up a defense and memory of the virus in question.

What is an mRNA vaccine and how does it work?

Vaccines that use messenger ribonucleic acid, or mRNA, rather than dead or weakened viral bodies have the same goal: The vaccine introduces and prepares the body’s immune system with a harmless part of the virus. Rather than using a dead or weakened part of the virus, mRNA vaccines provide a recipe that the body uses to build an identifying feature on the virus’ surface. In the case of SARS-CoV-2 (the virus that causes COVID-19), this identifying feature is the spike protein on the cell surface. The mRNA in the vaccine is taken up by our cells around the injection site, upon which our cell’s protein-reading machinery reads and converts the mRNA recipe into the SARS-CoV-2 spike protein. Once your cells begin producing the spike protein, your immune system perks up and begins to notice these foreign bodies. Your body builds up a specialized attack against the protein and commits it to memory, ready for a time when these immune cells might encounter the protein again, say, on the surface of the SARS-CoV-2 virus itself.

Dzwokai Zach Ma, a professor and researcher at UC Santa Barbara studying virus-host interactions in the Department of Molecular, Cellular, and Developmental Biology (MCDB), emphasized a few important points in this process: “(1) Since only the spike protein is generated inside the cells, the vaccine will NOT cause COVID-19. (2) The mRNA does not enter your cell’s nucleus, and thus, does not interact with your genomic DNA. (3) The mRNA will eventually be degraded and eliminated from your cells.”

These points help remind us of the safety of the mRNA vaccines and address some of the concerns that some might have about the vaccine. Moreover, while many of us have never heard of mRNA vaccines, Ma noted, “these vaccines have been the focus of active research for the last two decades. Pfizer and Moderna already had the infrastructure to conduct the research and production of the two mRNA vaccines we now have available in the United States.”

Indeed, the past two to three decades of research in mRNA vaccines perfectly positioned Pfizer and Moderna to quickly create, test and manufacture their mRNA vaccines.

“The conventional method where you have to produce, isolate, and purify a large amount of a dead/weakened virus or a recombinant viral protein, takes a long time,” Ma said. He explained that, in contrast, “you can standardize the large-scale production of mRNA vaccines. [Researchers] can also easily use the existing recipe to target any parts of the virus, including those of new variants as they arise.”

Ma continued, “mRNA, while quick to produce, is also quick to breakdown. That is why the two current vaccines need to be stabilized at very low temperatures (Moderna at -20°Celsius and Pfizer at -80°Celsius, and recently approved by the FDA for -20°Celsius for two weeks).”

In sum, mRNA vaccines have the same goal as vaccines that we are more familiar with. The differences between these mRNA and traditional vaccines are the molecular technologies that have been leveraged to make them.

Adenovirus vaccines:

Adenovirus vaccines are another kind of vaccine recently approved for emergency use by the Food and Drug Administration (FDA) and soon to be distributed by Johnson & Johnson. Oxford-Astrazeneca has also produced an adenovirus vaccine, but this brand has not been approved for use in the United States, as of March 14. Again, adenovirus vaccines — just like dead/weakened virus and mRNA vaccines — work to expose the immune system to a part of the SARS-CoV-2 virus in preparation for an encounter with the real virus. Quite similar to the mRNA vaccines, adenovirus vaccines insert the encoded recipe (this time in the form of DNA) for the SARS-CoV-2 spike protein into an adenovirus vector, or the shell of a type of virus that usually causes cold or flu-like symptoms. In this case, the vector has been disabled and cannot cause sickness.

After entering the cell, the viral vector utilizes the cell’s protein-making machinery to produce the spike protein, triggering your immune system to build up a defense. This vaccine uses SARS-CoV-2 DNA rather than mRNA to transfer the spike protein recipe. Again, the DNA is packaged within the adenovirus vector, which is disabled and lacks the genetic programming to replicate or cause infection. Both the switch to DNA, which is less prone to degradation than RNA, and the adenovirus vector make the vaccine more stable and amenable to refrigerator storage. In contrast to its Pfizer and Moderna counterparts, the Johnson & Johnson vaccine can handle some tougher conditions.

Adenovirus vaccines may sound familiar to those who are tuned in to the vaccine research world, as Johnson & Johnson recently created an adenovirus vaccine for the Ebola virus. Increasingly, the technology for mRNA and adenovirus vaccines will become a part of our vaccine lexicon as these methods have proven over time to be efficient, effective and safe.

Vaccine trials and FDA approval:

Scott Grafton, the UCSB campus COVID-19 coordinator and a distinguished professor in the Department of Psychological & Brain Sciences, spoke about vaccine trials during “The Science Behind COVID-19 Vaccines and Other Interventions” panel that was hosted by The Current on Feb. 25. Grafton noted that “for the FDA to approve the vaccine, the maker has to show that it prevents disease 50% of the time. All three currently available vaccines are all greater than 90% effective at protecting against hospitalization, severe disease and death — way above the low bar set by the FDA,” Grafton said in reference to the Moderna, Pfizer and Johnson & Johnson vaccines. He continued, “The two RNA vaccines are also 90% effective at reducing or preventing mild and moderate illness, while the J&J is comparatively 66% effective.”

One common misconception about the current COVID-19 vaccines is that the process of their approval was too speedy. As we just learned, researchers have responded to this concern by emphasizing the existing research in mRNA vaccines and the ease of mRNA production. Medical professionals have also emphasized the bureaucratic prioritization of this vaccine production and the prevalence and virulence of the COVID-19 virus for trials and testing.

Lynn Fitzgibbons, physician and infectious disease specialist for Cottage Health, said, “We’ve never had groups like the FDA and other branches of regulatory agencies work around the clock, making sure that all avoidable delays were avoided … In our lifetime, we’ve never had the ability to get 100,000 people signed up for a vaccine clinical trial within a month the way that our vaccine manufacturers were able to do last year.”

Once a vaccine is in the stage of clinical trials, vaccine approval is based on the proportion of infected versus non-infected participants. The number of infected trial-participants needs to reach some threshold in order to prove efficacy. Ma explained, “In the past when you want to test the efficacy of a vaccine, you have to wait for your patients to experience natural infection rates. Years down the line you can collect enough data for vaccine approval. Due to the prevalence of COVID-19 right now, many people in the trials got infected in a short amount of time. This shortened the period to determine the efficacy of these vaccines.”

Thus, the usual delays in vaccine trial sign-ups and vaccine approval have not been an issue due to the seriousness of the pandemic and the prioritization of these trials. The high prevalence and infection rate of COVID-19 not only made vaccine trials a priority for agencies like the FDA, but it also created the conditions under which the vaccine could be quickly tested for efficacy. No steps were skipped. Rather, the virus itself created the conditions for speedy vaccine approval.

Herd Immunity:

For the same reason many of us get the annual flu shot, the goal of COVID-19 vaccination and immunization is to protect yourself and the people around you from getting sick.

“Young people can still get COVID-19 and you never know how severely your body will react to the virus,” Ma said. “And as we know, even if you have mild or no symptoms, you can still pass it on to others. In addition, there is increasing evidence suggesting that a fraction of people infected by SARS-CoV-2 may experience long-lasting symptoms.”

Courtesy of Wikimedia Commons

When our government officials talk about returning to life without COVID-19 restrictions, they often refer to herd immunity as some benchmark of community safety. Herd immunity refers to the inability of the virus to move from person to person due to a high proportion of pre-existing immunity in the population from vaccination or previous infection. Thus, immune people act as barriers against the virus for the less common person that is not vaccinated and has never encountered the virus. When it comes to COVID-19, Ma said, “It is estimated that 70-90% of the population would need to either get vaccinated or contract COVID-19 in order to achieve herd immunity.”

This ballpark figure of approximately 80% of the population was also confirmed by Ali Javanbakht, physician and medical director at UCSB Student Health. Javanbakht said, “[This timeline] depends on people choosing to get vaccinated, what types of variants we have circulating and how quickly those variants circulate. If all goes perfectly well, it is possible to achieve herd immunity before winter 2022 but there are too many variables at play to say that with any amount of certainty.”

These time estimates for herd immunity are difficult to pinpoint — largely due to the unpredictability of human behavior and the production and ongoing approval of new vaccines. We cannot safely and quickly reach collective herd immunity if the majority of people choose not to be vaccinated. Ultimately, by getting vaccinated and gaining immunity against the virus, you are taking yourself out of the pool of potential hosts for the virus — slowing its spread and keeping the people around you safer. Additionally, limiting the pool of potential hosts for the virus actively slows the production of SARS-CoV-2 variants.

Variants:

Another concern people have about the vaccine is its relative efficacy in the context of the rising number of SARS-CoV-2 variants. Importantly, we must understand that variants are a common phenomenon with viruses. Carolina Arias, a professor and researcher in the MCDB department at UCSB, noted during the Feb. 25 COVID-19 vaccines panel that “variants are the natural evolution of the virus. As the virus replicates its genetic material, it accrues mutations with its reproduction, leading to new strains and variants.”

SARS-CoV-2 is not unique in having variants. Rather, this is a common phenomenon that may be cause for booster shots and even annual shots into the future. Stuart Feinstein, another UCSB MCDB professor and researcher on the COVID-19 vaccines panel, noted the familiarity we have with this situation: “We get a flu shot every year to account for new strains of the flu.”

Despite these new variants, the Moderna, Pfizer and Johnson & Johnson vaccines are still effective at reducing the severity of COVID-19 infection. In fact, getting vaccinated is the first line of defense against new variants. Said Javanbakht, “Thus far, it looks like all the variants identified will be covered by the current vaccines. So the race is on to get people vaccinated before new variants emerge that might not respond as readily to the current vaccines.”

Testing for variant strains of SARS-CoV-2 in Santa Barbara County has been limited. Our ability to understand the exact prevalence and potential impact of COVID-19 variants on vaccine efficacy is unknown, but this is an active area of research for Santa Barbara agencies. “We have an exciting new project underway to sequence local samples that’s a collaboration between Cottage, the Public Health Department, and Professor Arias’ virology lab at UCSB,” Fitzgibbons said.

Allergy concerns and delayed reactions:

Many may be concerned about potential allergic reactions to the COVID-19 vaccines. For the most part, there have been relatively few reported incidences of COVID-19 vaccine reactions. Ma said, “Common side effects right now include a sore arm, swelling at the injection site. You may get chills, muscle aches. You may develop a fever. Those effects are a sign of an activated immune system — or the vaccine at work. What people should pay a bit of attention to is the development of severe allergic reactions, or anaphylaxis.”

Anaphylaxis is an extreme, life-threatening allergic reaction in the body that develops in seconds to minutes as a result of allergen exposure.

At the time of the “Science Behind COVID-19 Vaccines and Other Interventions” panel, about 45 million people in the U.S. had been vaccinated. Grafton said, “If you vaccinated all of the people in Santa Barbara County — 450,000 people — two, maybe three people would experience anaphylaxis, or severe allergic reactions. Compare that to the 9,000 people that would experience anaphylaxis to peanut allergies or bee stings in the population.”

Arias emphasized: “The safety of these vaccines are under heavy scrutiny by different entities like the FDA and CDC. In the eight months since the first administered vaccines in clinical trials, we are not seeing reports of serious delayed adverse effects. It’s looking like these vaccines are safer and safer as time goes by and as more people get vaccinated.”

The Centers for Disease Control and Prevention (CDC), as well as several researchers and physicians interviewed for this piece, recommends that you check the ingredients list of all vaccines if you have any known allergies. This information for all three currently available vaccines can be accessed on the CDC website. If you have had allergic reactions to vaccines in the past, you should consult with your physician about getting the COVID-19 vaccine. If you have specific concerns about pregnancy or breastfeeding, it is again recommended that you consult with your physician before getting vaccinated. If you have a severe allergic reaction to your first dose of an mRNA vaccine, it is recommended that you do not get the second dose.

Fitzgibbons said, “The CDC website is a great place to start [to get infomed]. I would recommend going into the health care provider section of the CDC website, where there is information regarding some of the scientific studies if people want to look at the exact references themselves.”

For more UCSB-specific COVID-19 updates, Javanbakht said, “The campus COVID-19 webpage has good content and links to other resources.”

In the interim before you get vaccinated:

The majority of the adult population of Santa Barbara County and UCSB students are grouped in vaccination Phase 3, which targets the general population. Many have wondered when this group will have access to the vaccine. Regarding this timeline, President Biden said in his White House address on March 11th, “I will direct all states, tribes, and territories to make all adults 18 years and older eligible to be vaccinated no later than May 1.”

For the general population that is not at risk for serious COVID-19 infections, it may be some time before the county reaches Phase 3. In the meantime, we all need to stay focused on the common goal of keeping our communities safe and healthy. As much as we’d like to plan for the day when we will be back on campus and back in crowded lecture halls, we need to stay vigilant. As of March 14, 2021, new cases in California still exceed 2,000 per day. The severity of the pandemic has not decreased despite our readiness to get to post-COVID-19 life.

Social distancing and mask-wearing (maybe even ramping up to double-masking) will continue to be some of our best tools for slowing the spread of COVID-19. Most importantly, educating ourselves and others about the vaccine is essential. Our communities will not safely and quickly reach herd immunity — and thus life without COVID-19 restrictions — without vaccination.