What Is a Booster Dose?

A booster dose is an additional administration of a vaccine to make it fully effective or maintain the patient’s immunity. Some vaccines need to be given in a series because a single shot is not sufficient. With others, the body gradually loses immunity over time if it is not exposed to the antigen, and a booster is required essentially as a sort of reminder to the immune system. Medical organizations maintain careful vaccine and booster dose schedules with recommendations and it is advisable to follow them for vaccines to be as effective as possible.

Some booster doses are given after a few weeks, while others may be given months or years after the initial vaccination. The variation in vaccine scheduling is a result of the different proteins involved in the production of vaccines. Each interacts differently with the immune system, and the body may need varying amounts of exposure to the carefully processed antigen to develop immunity.

When a vaccine is recommended in a series, patients must receive the whole series to be effectively immunized. If they miss the booster doses or schedule them too far apart, the vaccine may not work. A doctor can request a blood test to determine if the patient’s immune system is sufficiently sensitized. If the results are negative, another booster or a repeat of the series may be needed. When possible, physicians may recommend giving vaccines in combination so patients can receive several at one appointment.

In other cases, people may need a booster shot after an initial vaccine has started to wear off. A common example is tetanus. About 10 years after people receive the initial vaccine, they will need a booster to ensure continued protection against the disease. Boosters can also be advised after exposure to an antigen to add protection; someone who steps on a nail and hasn’t had a tetanus vaccine recently, for example, could get a booster.

Patients who aren’t sure about when their boosters are due can ask for assistance. Doctors maintain vaccination records on their patients and can check them to determine which boosters may be required. It is also possible to request a copy of the vaccination record for future reference. If vaccines are missing from the record, the patient may need a blood test or a booster dose to guarantee protection, even if patients think they were vaccinated for the disease in question.