Often people fall ill or have symptoms like fever, chills, body pain among others for a couple of days after taking a dose of the Covid-19 vaccine, however, this is not a cause for concern and in fact, a positive sign. These are signs that your body is building protection against the disease.
However, while there are many who don’t experience any symptoms after getting a dose of the vaccine, does this not mean the vaccine dose you got is ineffective, according to a study published in JAMA Internal Medicine. The study says that those who don’t experience effects after getting a shot of an mRNA Covid-19 vaccine still develop an effective antibody response.
The researchers said those who received a vaccine dose “mounted a strong antibody response to the spike protein…independent of vaccine-induced reactions”. This brings about the question, how does an immune response work? Why do some end up feeling worse than others?
Vaccines expose our immune systems to an antigen — part of a pathogen — which triggers an immune response. The antigen is often an inactivated, weakened, or just a part of a virus such as a spike protein. The spike protein of SARS-CoV-2 is what helps the virus attach itself to human cells.
Some Covid-19 vaccines deliver the antigen directly to the body, whilst, other vaccines such as those made by Pfizer, Moderna and AstraZeneca provide a genetic blueprint that tells the immune system how to make the SARS-CoV-2 spike protein using your own body’s cells.
Pfizer and Moderna vaccines use messenger RNA or mRNA — a single strand of genetic material —which is covered in a protective fatty coating. The AstraZeneca vaccine, however, uses a weakened version of the common cold virus carrying a double-stranded DNA to do this. The virus is made in such a way that it does not replicate and give you the common cold.
When the shot is injected into the arm, the muscles in our arm immediately start to make those spike proteins and as this happens, the innate immune system is already detecting this development or any damage or cells. The mRNA or DNA tricks the innate immune system into thinking it has detected a virus.
This is when the immune system sends in white blood cells, these cells have multiple functions, one is to destroy foreign cells, eat up dead cells and collect samples of antigen. This antigen helps the body develop an adaptive immune response in case of further infection. These cells trigger the release of a group of proteins called cytokines that help signpost other immune cells to the site where the injection was given.
This response by the immune system happen over a matter of hours or a few days and symptoms like fever and the flu are healthy signs that your immune system is working as it should. However, the study has found that those without flu-like symptoms do develop a robust antibody response. Flu-like symptoms in your body will appear only if the inflammatory signal produced by your immune system is strong enough.
Once the immune response has begun, B-cells produce antibodies that catch antigens and stop it from infecting further cells. Helper T-cells assist B-cells to make antibodies as effective as possible and within a week or two, you will have antibodies to fight SARS-CoV-2.