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The 411 on the vaccines in the fight against COVID-19

Intensive Care Unit nurse Kathy Brady looks on as Pharmacist, Courtney Mattley, left, draws the first dose of Pfizer BioNTech, Covid-19 vaccine before administering it to Brady at Henry Mayo Newhall Hospital in Valencia on Thursday, 121720. Dan Watson/The Signal

There are three forms of the COVID-19 vaccine, two of which remain in active use as of the publication of this article: Moderna and Pfizer.

The third, Johnson & Johnson’s inoculation effort, is now under a new microscope that’s been discussed by local, state, national and world health officials, due to the widespread demand for vaccines.  

Here’s some information to help understand the differences, some of the possible side effects and why there’s been concern for the effects of a vaccine that’s caused a severe reaction in only the tiniest percentage of its recipients.

Moderna & Pfizer

Moderna and Pfizer have both developed vaccines that require two doses of the shot, and both work in similar ways, according to the experts. 

“The Moderna and Pfizer are called mRNA vaccines,” said Dr. Elizabeth Hudson, the chief of infectious diseases for Kaiser Permanente Panorama City Medical Center. “The J&J vaccine is an adenovirus vector vaccine.”

The difference?

“The way that the technology is, is that the mRNA is a sequence of a protein that basically tells the body how to make the ‘spike protein’ of the Coronavirus, and they wrap that information in a liquid molecule and put it in the vaccine and then they give it to you through a shot,” said Courtney Mattley, the pharmacy clinical coordinator for Henry Mayo Newhall Hospital. “Ultimately, your body is making the spike protein of the Coronavirus, which is the little spikes you see on the outside of all these pictures of the Coronavirus. 

“So, that’s your body, making a piece of the virus so that eventually, if you actually get the real virus, they can acknowledge what that is and know what to do,” she explained, “because you’ll have already been exposed to it.” 

It is through this creating of a small version of the disease within you that, according to the experts, results in arm pain, or even what is known as “a classic presentation.” The first dose is generally associated with the arm pain, while the second dose can sometimes result in flu-like symptoms in some patients.  

“It’s your immune system being exposed again and actually mounting an immune response, so you feel almost as if you were exposed to something that makes you sick, because you’re making that same reaction,” said Mattley. “But you’re not actually having an infection.”

Johnson & Johnson 

Johnson & Johnson’s vaccine is not an mRNA vaccine, but rather, as previously mentioned, is an adenovirus vector vaccine. 

In layman’s terms, this roughly equates to meaning that it is a traditional virus-based technology that delivers instructions on how to defeat COVID-19. However, it cannot replicate in your body, and will not give you an infection. 

“Johnson & Johnson is linked to a different virus, like a weakened virus that cannot affect you,” said Mattley. “Ultimately, you get the same result — you get the spike protein being made by your body, and then your body knows what to do as far as antibodies and what to do if exposed to the real virus.” 

Both injections of the Moderna and Pfizer contain the same exact solution within them, with the body experiencing equal exposures both times. 

Johnson & Johnson differs in that it is one shot, but because of its approach, it’s easier to store and allows for people to be fully vaccinated if they are at risk of not returning for a second shot. 

Yale Medicine officials released a report in February comparing all three vaccines and their ability to produce to the desired effect of immunization, stating Pfizer has a 95% efficacy of preventing infection; Moderna has 94.1% in people before infection; and Johnson & Johnson has 72% overall efficacy. It’s important to note that all three of these vaccines are highly effective, according to officials. The differences in reported effectiveness are due to the different locations and time of the pandemic that the vaccine trials were held.  

Rare concerns

On Tuesday, both the Centers for Disease Control and the Food and Drug Administration recommended a pause on the administration of the Johnson & Johnson vaccine in order to conduct further investigation.

“It’s a rare blood clot that also is associated with low platelets which is a strange thing to happen, so that basically means you’re (at a) higher risk of clotting and high risk of bleeding at the same time, which is what makes it a special circumstance,” said Mattley. “So, that’s why they’re giving it more attention than just a normal blood clot.”

“There was just as many people who disagree with pausing the vaccine because six is extremely, extremely rare out of 7 million, I mean that’s such a low number,” she added. “But because of the fact that it’s such a rare circumstance of the type of blood clot that that it is, and the fact that we’re doing this mass vaccination across the world, they’re just not wanting to take the risk.” 

The Advisory Committee on Immunization Practices, or ACIP, of the CDC has yet to issue an update about when the use of the Johnson & Johnson vaccine might resume.   


There are a number of myths circulating around the vaccines, from the vaccines causing a change in your DNA to it resulting in infertility. 

“It’s literally scientifically impossible for mRNA to be incorporated into your own body’s DNA,” said Mattley. “It does not enter the nucleus, which is where our DNA is, and it also gets broken down extremely, extremely fast by our own body, which is why you have to freeze it at these ultra-low temperatures to make it stable.”

The second rumor that she and her colleagues have been trying to put down is a potential fertility issue. 

“Now, of course, we have no long-term data, but we have no scientific reason to believe that it would cause infertility,” said Mattley. “There’s a ton of people in the studies who have become pregnant while they were getting studied or as soon as the study was over.” 

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