The World Health Organisation says vaccines undergo three phases of human clinical trials to test for safety and efficacy before they are authorised for use.
WHO noted that vaccine efficacy measures the reduction of risk in vaccinated people compared to unvaccinated groups.
The UN body made this known in a short video clip posted on its official Twitter account in Nigeria @WHONigeria.
It said, “accines are first tested on animals in pre-clinical trials.
“They then undergo three phases of rigorous human clinical trials to test for safety and efficacy before they are authorised for use.”
The organisation said vaccine efficacy measures the reduction of risk in vaccinated people compared to unvaccinated groups.
“So, if a vaccine has 92 percent efficacy, it means you are 92 percent less likely to fall ill after the jabs.
“Thanks to vaccines, smallpox was eradicated. And last year, the African continent was declared free of wild polio.
“So now you know what ‘safe and effective’ means. If you have the opportunity, please get the jab.”
Earlier, the organisation defined a vaccine as a tiny, weakened, non-dangerous fragment of a pathogen- the germ that causes a disease – and the part included is called the antigen.
It added that vaccines trigger an immune response in the body to build the right antibody against pathogens.
“Being vaccinated won’t give you the disease but it will trigger an immune response in your body and teach it to build the right type of antibody to protect you in the future against the pathogens.
“That way, if and when your body encounters the real pathogen, later on, it already knows how to spot and fight off the pathogen before it can cause disease,” WHO said.