How Many Booster Shots Can the Body Take?

booster shot

With the FDA recommending booster shots of the approved COVID-19 vaccines, it seems like the time in between booster shots and recovery time keeps getting shorter and shorter. Plus, many questions arise when it comes to taking the vaccine with other medications or other vaccines. Parents sometimes worry that their child’s immune system will not be able to cope with receiving several vaccines at once. And some adults are worried about getting multiple booster shots after six months, five months or whatever the timeframe is now.

So should we be concerned if we are taking booster shot after booster shot? First, we need to look at how long our bodies have been exposed to vaccines.

Your Vaccine History Since Birth

The majority of children are given shots (vaccines) at a young age because this is when they are at highest risk of getting sick or dying if they get these diseases. In fact, many school systems won’t allow children in school unless they have vaccines for diseases that used to be deadly (Hep B, polio, whooping cough, etc). Newborn babies are immune to some diseases because they have antibodies they get from their mothers, usually before they are born. However, this immunity lasts a few months. Most babies do not get protective antibodies against diphtheria, whooping cough, polio, tetanus, hepatitis B, or Hib from their mothers. That’s why the CDC says it’s important for the child to get the vaccine first before the child is exposed to the disease.

Vaccines contain weakened or killed versions of the germs that cause the disease. These elements of vaccines, and other molecules and micro-organisms that stimulate the immune system, are called “antigens.” Babies are exposed to thousands of germs and other antigens in the environment from the time they are born. When a baby is born, his or her immune system is ready to respond to the many antigens in the environment and the selected antigens in vaccines.

How the Body Reacts to Vaccines All at Once

Approximately 90%-95% of recipients of a single dose of certain live vaccines administered by injection at the recommended age (i.e., measles, rubella, and yellow fever vaccines) develop protective antibodies, generally within 14 days of the dose. For varicella and mumps vaccines, 80%-85% of vaccines are protected after a single dose. However, because a limited proportion (5%-20%) of measles, mumps, and rubella (MMR) or varicella vaccinees fail to respond to 1 dose, a second dose is recommended to provide another opportunity to develop immunity (4). Of those who do not respond to the first dose of the measles component of MMR or varicella vaccine, 97%-99% respond to a second dose.

Scientific data show that getting several vaccines at the same time does not cause any chronic health problems. A number of studies have been done to look at the effects of giving various combinations of vaccines, and when every new vaccine is licensed, it has been tested along with the vaccines already recommended for a particular aged child.

The recommended vaccines have been shown to be as effective in combination as they are individually. Sometimes, certain combinations of vaccines given together can cause fever, and occasionally febrile seizures; these are temporary and do not cause any lasting damage. Based on this information, both the Advisory Committee on Immunization Practices and the American Academy of Pediatrics recommend getting all routine childhood vaccines on time.

From birth onwards, a baby comes into contact with millions of germs every day. Babies’ immune systems are working all the time to protect them against bacteria and viruses in the environment. Vaccines represent a very small challenge to the immune system when compared to this. According to the University of Oxford, each millilitre of blood contains ten million B cells, the white blood cells that are associated with the immune response. It is estimated that this would be enough to cope with multiple vaccines.

According to, with rare exceptions, all vaccines can be administered at the same visit. There is no upper limit for the number of vaccines that can be administered to adults during one visit. ACIP and AAP consistently recommend that all needed vaccines be administered during an office visit. Vaccination should not be deferred because multiple vaccines are needed. All live vaccines (MMR, varicella, live attenuated influenza, yellow fever, and oral typhoid) can be given at the same visit if indicated. If live vaccines are not administered during the same visit, they should be separated by 4 weeks or more.

When Should You NOT Combine Vaccines

As a general rule, there are very few vaccines that can’t be co-administered, says L.J Tan, MS, PhD, the chief policy and partnership officer at the Immunization Action Coalition in St. Paul, Minnesota.

Vaccines commonly administered together include

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