What our experts say
A booster shot is an additional dose of a vaccine that people get after they have received their first dose.
Booster shots re-expose our bodies to the part of the vaccine that protects us against disease. They increase immunity to a virus or bacteria through a process called immunological memory. Immunological memory is our body’s ability to recognize and provide responses to previously encountered foreign invaders like COVID-19.
For example, tetanus shot boosters for adults in the United States are recommended every ten years. Research has shown that after ten years after a tetanus shot, our bodies start to forget how to fight off tetanus. The booster shot reminds our immune system to attack a virus or bacteria.
Doctors can prescribe booster shots for people of all ages. Sometimes they can be especially important for people with specific medical conditions, lifestyles, travel patterns, or occupations. Some of the vaccine boosters that children need include Hepatitis A and B, Tetanus, Diphtheria, Pertussis, Haemophilus influenza type B, Chickenpox, Measles, Mumps, and Rubella. In addition, teens or adults need Tetanus, Diphtheria, Pertussis, shingles, varicella, Measles, Mumps, Rubella, and most recently, Covid-19 vaccine boosters.
Context and background
For many viral and bacterial diseases, prevention is the most effective and best form of treatment that we have. Vaccines help protect us from diseases. However, once we have been vaccinated for a particular disease, we might think we are always safe from it. That is not necessarily the case. For some diseases, that protection wears off over time. In other cases viruses change or mutate, making the vaccine less effective against the newer version of a pathogen. That is why for many vaccinations, we need more than one vaccine dose.