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Extended interview: expert explains how COVID-19 vaccines work and side effects after injections
Dr Williams Moss, epidemiologist and executive director of the Johns Hopkins International Vaccine Access Center, explains how mRNA vaccines from Pfizer and Moderna work and why side effects are more likely after the second dose.
As the COVID-19 vaccination campaign continues and more people receive their second dose, many have reported that it is causing more intense side effects than after the first. But vaccine experts say this news is both normal and expected.
“It’s a sign that your immune system is working,” said Dr Williams Moss, epidemiologist and executive director of the Johns Hopkins International Vaccine Access Center.
To date, more than 35 million vaccines have been administered in the United States, and nearly 7 million have received their second and last dose, according to the United States Centers for Disease Control and Prevention.
Side effects from vaccines used in the United States, developed by Moderna and Pfizer-BioNtech, are normal signs that your body is building up protection. The CDC says flu-like symptoms are to be expected and can include fever, chills, headache, muscle aches, and fatigue. Some people may experience pain and swelling in the arm at the injection site. All side effects should go away within a few days.
In vaccine trials for Moderna and Pfizer, side effects were more common after the second dose. Moss said some may have had minimal symptoms or no symptoms from the first dose, but will experience side effects after the second because their immune system is already primed – resulting in a more intense inflammatory response the second time the medication is given. gas.
FILE – A woman receives a Pfizer COVID-19 vaccine at a vaccination center established at Triton College in River Grove, Ill. On February 3, 2021 (Photo by KAMIL KRZACZYNSKI / AFP via Getty Images)
Users of V-safe, the CDC’s tool for reporting vaccine side effects, reported more side effects within a week of their second injection, compared to the first.
Mark Sussman, who recently received his second dose of the Moderna vaccine, said he had felt sick for about a day and a half.
“Chills, shortness of breath, muscle aches, just general pain,” Sussman described to FOX 5 DC, days after receiving his second injection. Sussman added that it was not a “full-blown flu,” but the side effects lasted for about 36 hours.
But not everyone experiences side effects. Sussman’s mother also recently received a second dose of the Pfizer vaccine and was feeling well.
How does the COVID-19 vaccine work and why do we experience side effects?
There are advanced proteins on the surface of SARS-CoV-2, the virus that causes COVID-19, which are essential for the virus to bind to cells in the body and replicate. All COVID-19 vaccines developed work to induce an immune response against the spike protein, primarily through antibodies.
Moderna and Pfizer vaccines administered in the United States are mRNA vaccines. This is a new technology but not unknown, as scientists have been working on mRNA technology for over a decade.
Instead of injecting the virus, Moss explained that mRNA vaccines work by injecting a “recipe” for the spike protein, or genetic code, causing cells to produce the spike protein.
“Through this mechanism, our own cells making the spike protein, so what happens is our immune system will see that protein and recognize it as foreign,” triggering an immune response, he said.
This immune response is widely known as inflammation, which can lead to side effects such as redness, swelling, and tenderness at the injection site. It can also mean a wider systemic response in the body, such as fever, headache, muscle pain, joint pain, or fatigue.
“A number of things are happening when it comes to inflammation, but this is really a sign that our immune system recognizes that there is a foreign protein in our body and is preparing to fight and fight it. ridding, “Moss said.
Why would some people experience more side effects after the second dose?
As part of the body’s immune response, it builds memory cells called T cells and B cells. If a virus or foreign substance re-enters our body, such as the second dose of the mRNA vaccine, it is a booster. for the immune system.
“Basically that second dose is like, ‘Hey, I know a month ago you saw this spike protein. I will remind you once again what she looks like so that you are really ready to attack her. “” Moss explained.
Moderna and Pfizer vaccines come in two doses, separated by 28 and 21 days, respectively.
The first dose of the vaccine triggers the immune system, building an army of cells. As a result, Moss said the second dose then generates a stronger immune response – hence the possibility of stronger side effects.
“We have a lot more cells available to attack him,” Moss explained. “But that’s why the inflammation can be more severe with the second dose because our immune system is sort of already prepared, so you get an even more intense inflammatory response.”
Does the vaccine still protect you if you don’t have side effects?
While side effects are usually a sign that the body’s immune system is working, those who feel well after receiving the vaccine are certainly protected as well.
“People who don’t have moderate or severe side effects from the vaccine can still have a very protective immune response. They just don’t, for various reasons, have this intense inflammatory response,” Moss said, citing a combination of genetics and history of exposure.
Why is the second dose of COVID-19 so important?
The dose of two injections of Pfizer and Moderna is what has been shown in clinical trials to be 94% or 95% effective in preventing symptoms of COVID-19. Although some protection is provided by a single dose, protection may be much shorter, although it is uncertain.
In January, the United States Food and Drug Administration said extending the time between doses or skipping the second would be “premature and not firmly anchored in the available evidence.” The agency reiterated the importance of continuing the two-dose regimen at the 21 and 28 day study intervals.
Dr Anthony Fauci, the government’s top infectious disease specialist, also said this week that the United States will “follow the science” of its clinical trials and continue to administer the second doses of the Pfizer-BioNTech and Moderna vaccines in the recommended timeframes.
Fauci was responding to a debated strategy the UK used to delay the second shot so it could quickly protect more people with a first dose. Pfizer, one of two vaccines approved in the country, did not approve the decision to space the time between doses.
Fauci says US should stick to current 21 and 28 day vaccination intervals for Pfizer, Moderna
Dr Anthony Fauci said the United States should stick to data showing optimal results by increasing Pfizer vaccine to 21 days and Moderna to 28 days, despite AstraZeneca’s studies of interval extension.
More than 458,000 Americans have died from the virus, a higher death toll than during all of World War II. Almost 27 million people in the United States have contracted it, some with even more serious long-term complications.
“I often say that the basic problem for most people … is that they underestimate the risk of the disease and overestimate the risk of the vaccine,” Moss said. “A day or two of discomfort is, in my opinion, a valid compromise to be protected against disease.”
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This story was reported from Cincinnati.
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