Some people have expressed concerns that the Pfizer vaccine may have long-term side effects. Although it is always important to consider the risks and benefits of any medical choice we make, there is no vaccine that has caused late-onset side effects (beginning more than 2 months after receiving the vaccine). All vaccines are made to disintegrate safely in your body. Vaccines introduce a non-harmful ingredient that looks like the true virus or bacteria, allowing your body to build antibodies against the virus/bacteria without getting infected.
For the Pfizer vaccine, the non-harmful ingredient is mRNA. This acts like a recipe that our body uses to build protein. This protein is harmless but does look exactly like the protein on the outside of the novel COVID-19, so our antibodies can be prepared if it sees the real virus. mRNA, however, is literally used up as it is read by the body. In fact, the end of the mRNA recipe has instructions to break down the mRNA and stop the production of the protein.