Man is born very helpless, having a lot to do. And just as you should learn skills like walking, your immune system should learn to defend against infections. As time passes, your immune system matures through various stages, progressing along the way as you go from crawling to standing, walking, and running.
This process is one reason scientists study the immune response to a vaccine in different age groups, and why, for example, COVID-19 vaccines are administered separately in children aged 5-11 years and 12-16 years. needs to be tested. Doctors want to use the vaccine dose that provides the best protection with the fewest side effects. And that would depend on how developed the immune system is, depending on how it’s working – something you can’t really tell from the outside.
I’m an immunologist, and here’s the way I explain to my pediatric and adult patients how vaccines work in people of all different ages.
two parts of the immune system
The process of immune maturation begins soon after birth.
When you are born, your main immune defenses come through antibodies shared by your mother through the placenta and breast milk. They provide what is called passive immunity. Newborns’ adaptive immune system — the part of your immune system that will make your own antibodies — isn’t actually activated yet. The process begins immediately, but it can take years for the adaptive immune system to reach full maturity.
Luckily you’re also born with an innate immune system – and it remains in place throughout your life. It doesn’t need to learn to fight infection and promote health as the adaptive immune system does. People without an innate immune system will get sick much faster and more often.
The innate immune system starts with your skin and mucous membranes. Should a germ cross those physical barriers, it has enzymes that wait for foreign organisms to break down. Also special cells are on the lookout for anything that is not you to kill the intruder, while other cells called phagocytes capture the invaders.
So the innate immune system is your body’s first response. It buys you a little time. Then your adaptive immune system comes and joins the fight.
When you become immunized through a vaccine or infection, your adaptive immune system begins to actively make your own antibodies. They are proteins that act like suction cups and stick to viruses or bacteria to help the body get rid of germs faster and prevent the infection from spreading. Antibodies are specialized to recognize and kill a particular intruder.
The adaptive immune system may learn a new infection or miss one it hasn’t seen in a long time.
Vaccines account for immune development
In the same way a baby learns to walk, even if you don’t make stairs and pool areas safe for them, your immune system can learn to suppress an invading virus without a vaccine – but the potential for injury is much greater.
Vaccines work by triggering the creation of antibodies that will recognize a specific germ and work to fight it in a safer way than if you first got the infection without it. How well a vaccine works is a combination of how many antibodies you produce in response to it, how effective they are, and the vaccine’s safety.
As researchers work to fine-tune vaccine doses for different age groups, they need to be aware of which parts of the immune system are online and which parts are fully active in people at each developmental stage. are not. This is part of the reason some vaccines – such as those for COVID-19 – are tested and approved on different schedules for adults, teens, children and infants.
Many vaccines for babies are given as a series – meaning they get the same shot multiple times over the course of a few months. A child’s adaptive immune system is prone to forgetfulness or not hearing at this age – in the same way as a child tries to stand and walk. With each exposure, every aspect of the immune system becomes stronger and better equipped to defend against potential infection.
After age 4 and through young adult life, your immune system is more reactive and less likely to forget. It is no coincidence that this is when people get most of their allergies. For the COVID-19 Pfizer vaccine, researchers found that children ages 5 to 11 had similar immune and protection responses at a third of the doses used for children 12 years of age and older.
When studying vaccines, scientists start with patients between the ages of 18 and 55. Their adult immune system has matured and they can be relied upon to reliably report any adverse reactions. Seeing what happens in an adult age group also helps physicians anticipate what might happen when one vaccine is given to others and to be on the lookout for these side effects in younger age groups.
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Around age 55 or older, the adaptive immune system begins to weaken and forgetful again, in some ways similar to that of an infant’s developing system. Fortunately vaccine boosters can provide a quick refresher for these older patients—like helping them avoid accidental falls after a lifetime of mastering walking and running.
In the end, vaccines provide the safest environment for the immune system to learn, and reducing dosages for different age groups helps ensure that each patient gets the job they need to complete.