I’m not a surgeon of rockets... but I would think that a strong reaction to the vaccine would indicate that you privy didn’t have a strong presence of anti-bodies to fight it off... I would love the docs on the board to chime in.
In this Q&A,
Dr. Melanie Swift, co-chair of the COVID-19 Vaccine Allocation and Distribution Work Group at Mayo Clinic, explains why vaccine side effects happen and what is known about symptoms following COVID-19 vaccination:
Why do people experience side effects from COVID-19 vaccines?
When we get vaccinated for COVID-19, we often experience some side effects. The reason that we get side effects is that our immune system is revving up and reacting. When you get sick, the same thing happens. Actually, a lot of the symptoms from illnesses that we get, like influenza and COVID-19, are actually not caused by the direct action of the virus, but rather by our immune system. Our bodies react, and that gives us these general symptoms like fever, achiness and headache.
Why are some people more likely to experience side effects after the second dose of a COVID-19 vaccine?
When you take two doses of a COVID-19 vaccine, the first dose is the first time for your body to see the spike protein that the COVID-19 vaccines produce, and your body begins to develop an immune response. But that happens slowly. Then when you come back with a second dose, your body is ready to attack it. Your body is primed by that first dose of vaccine. The second vaccine dose goes into your body, starts to make that spike protein, and your antibodies jump on it and rev up your immune system response. It's kind of like they've studied for the test. And it's acing the test.
How long could symptoms or side effects of COVID-19 vaccination last?
The vaccine side effects that we've seen in these large phase three trials resolve within about 72 hours of taking a COVID-19 vaccine. At most, those side effects can last up to a week. We really have not seen long-term side effects from COVID-19 vaccines beyond that, and that makes sense when you look at other vaccines. And we have a lot of experience with different vaccines. Long-term side effects are just basically unheard of in the vaccine world.
So with two months of follow-up data in people undergoing those clinical trials, and now even longer follow-up from the trials and our experience giving vaccines to the public, we really are not seeing any trend toward any long-term side effects.
Why does the second vaccine shot have stronger side effects?
The Pfizer and Moderna COVID-19 vaccines are both reactogenic vaccines, which means they are likely to cause side effects. This doesn’t mean, however, that everyone will have side effects, or that the vaccine doesn’t work if it doesn’t cause side effects.
The second dose of the Pfizer and Moderna vaccines is likely to cause more noticeable side effects. In both the
Pfizer and
Moderna vaccine clinical trials, more participants had symptoms like headache, fever, and body aches after the second dose.
The effects tend to be more intense after the second shot because of the way your immune system responds to vaccines. If you have never been exposed to COVID-19 and get your first shot of the vaccine, the virus protein that the vaccine causes your cells to produce, known as
the spike protein, is new to the body (this protein is harmless and will not infect you with the virus).
Your body recognizes the protein as an antigen — something foreign — and starts reacting to it with inflammation at the injection site. This is why the first shot very commonly causes arm pain.
The cells that cause inflammation in your arm after the vaccine also send signals that tell your body to create antibodies against the spike protein. This process can cause
inflammation in other parts of the body, leading to headache, fatigue, and fever after the first vaccine shot for some people.
When it comes time for the second shot, your body already has some antibodies and some cells that “remember” the spike protein from the first dose. When those cells see it again, they recognize it and
launch a stronger response very quickly. This response causes widespread inflammation that can lead to flu-like symptoms. The good news is that this process also creates many more antibodies, which help protect you in the future.
For those that have never been infected, the first vaccine primes the immune system and the second acts like a booster. For some that have already had COVID-19, the infection primes the immune system and the first shot may act like a booster. For these people, the first vaccine shot may cause more symptoms than for those that have not had COVID-19 before.
