Though vaccines are generally safe, they do come with possible side effects. Most of these side effects are mild and pose no actual danger.

Common side effects of vaccines

  • The most common side effect is redness and soreness around the vaccination site; such inflammation is to be expected anytime you’re poked with a needle.
  • It’s normal for kids to get a slight temperature. Raising the body’s temperature is one of the ways the body fights off pathogens, so it’s normal for kids to get an elevated temperature as their immune system kicks into gear. Call the doctor if it climbs above 100.4 degrees Fahrenheit.

How common are vaccine side-effects?

More than 95% of the time, kids sail through their shots with little more than a bit of fussiness, according to Renee Jenkins, president of the American Academy of Pediatrics. For the most part, statistics back up such a statement. Pain and swelling at the injection side can occur in around 65% of kids receiving their first flu vaccine. Other mild side effects such as a rash, fever, or other aches and pains can develop in anywhere from 5% to 15% of kids getting their vaccines. But severe side-effects, such as lifethreatening allergic reactions (on average no more than 100 cases per million) or seizures (generally no more than 300 cases per million) are rare. This means that around one out of every 3,333 kids have complications that go beyond mild side-effects, and 1 in 10,000 may have an allergic reaction.

Data from the CDC shows around 30,000 “adverse events” are reported by doctors and patients every year. Of these, 3,000 to 4,500 are serious enough to cause hospitalization. A small percentage of these pose a life-threatening condition, and in some rare cases, can even cause death.

So yes, vaccines can sometimes cause unique reactions in a small minority of children. Extreme reactions leading to death are extremely rare, literally less than l-in-a-million chance (even when an allergic reaction occurs it can usually be treated in time). So vaccines are not entirely without risk, but they are a much better risk than the diseases they protect against, which kill, disable, and maim children at far higher rates.

Vaccines & seizures

The DPT vaccine is known to sometimes lead to febrile seizures. Though media reports have revolved around parents who were worried their kids had suffered brain damage because of it, long-term follow-up studies found neither the vaccine nor the seizures caused any lasting damage. (!-laelle, 2021) See our information on febrile seizures for more information.

Questions being explored to improve vaccine safety

There are still some questions ….

Though the vaccination-autism link may be an imagined one, vaccines are capable of producing adverse events, just like any medical procedure. The purpose of a vaccine is to deliver dormant forms of virus which in turn cause a child’s immune system to attack these viruses, which brings about physiological responses. When the body fights off these benign invaders, the immune system keeps a “memory” of the viruses and the antibodies used to attack it, which in turn should give the child immunity against the real virus.

Though the viruses are benign, the immune system’s reaction is real, and sometimes, this extra reaction can cause or aggravate unrelated problems. In addition, like any other substance in the world, there are those who can develop an allergic reaction to the vaccine in the shots. Most often times this is minor redness or swelling at the injection site, but vaccines can occasionally cause reactions that are more severe.

Vaccine response
Vaccines trigger a bodily response. While this response is well understood, little is known about how the response itself can affect other unique physiology in the recipient. The body is its own ecosystem, with thousands of variables interacting upon it at any given time. While we know that A (vaccines) cause B (an immune response), little is known about how the other variables (C through Z and the thousands of other factors) may aggravate or interact with the immune response we’re creating.

Vaccine schedules
The current one-size-fits-all vaccine schedule, amazingly enough, has never been tested for maximum efficacy and safety. The NIH will look at the possibility of spacing out shots or delaying certain ones to minimize the risk.

Immune capacity
How much is too much? One of the biggest debates surrounds the sheer amount of vaccines given. Kids now face 38 shots against 15 diseases before they hit kindergarten. Many of these shots are given at one time, raising further concerns about the possibility of overwhelming a child’s immune system all at once. Babies nowadays receive up to 6 shots in one doctor’s visit against 8 different diseases.

As a baby leaves the womb, its immune system is basically a blank slate. While this changes within days as they are exposed to a variety of pathogens in their environment, there is still concern about how much is too much for a still developing immune system, and whether overloading it can cause hyperactivity that will overwhelm and harm the child. In 2002, the Institute of Medicine concluded that giving babies 20 shots against 11 diseases before the age of 2 DID NOT raise the risk of juvenile diabetes, which was thought could be a result of a hyperactive immune system. Yet they couldn’t prove or disprove an increased risk for allergies and asthma. Regardless, many question the wisdom of hitting a child’s immune system with so much all at one time.

The genetic component
Not all children are the same. The question is still open as to whether certain groups of children with specific genetic defects might be more susceptible to harm from vaccinations, such as the court ruled was the case with Hannah Poling, whose undiagnosed mitochondrial disorder may have developed into autism as a result of the nine vaccinations she received all at once. Notes Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, “If we can show that individuals of a certain genetic profile have a greater propensity for developing adverse events, we may want to screen everyone prior to vaccination.”

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