Experts have previously said it’s ‘normal’ to feel unwell after getting one of the two Covid jabs being rolled out in the UK.
Side effects from the jabs currently being administered are ‘very common’ according to official guidance.
But some are lucky and don’t have any side effects from the vaccine.
Professor Martin Michaelis and Dr Mark Wass from the University of Kent explain to Express.co.uk: “Although this may feel like the real disease, it is actually the response of the immune system to the vaccine.”
None of the vaccines currently available around the world contain the live virus – so cannot give you Covid-19.
They continued: “They use different strategies to present just parts of the virus to the immune system and they do not cause an infectious disease.
“Whilst the placebo effect is associated with clinical improvements seemingly caused by psychological effort from the patient, they can also induce negative responses, the ‘nocebo effect’.”
“Negative responses are known to have resulted in the discontinuation of therapies in up to 25 percent of patients in placebo arms of clinical trials.
“Sometimes, side effects are higher in the placebo group than in the group receiving the active treatment.
“So, for some vaccinated individuals, the knowledge that they have been vaccinated may be sufficient to drive side effects.
“Ultimately, side effects associated with COVID-19 vaccinations are not a sign of the disease.
“COVID-19 vaccines are not capable of infecting anyone with SARS-CoV-2, the coronavirus causing COVID-19.
“Negative results are likely caused by the immune response to the vaccine, or the knowledge that we have been vaccinated acting as a ‘nocebo’.”