What’s the Deal With the Recommended Vaccine Schedule?

Many people assume that the current vaccine schedule was not created for the benefit of the baby but for the preference or convenience of the medical industry—and, if so, that there could be an alternative vaccine schedule that is actually better for the baby.

But that is not the case. The current U.S. vaccine schedule is the product of thoughtful and informed collaboration among specialists in pediatrics, infectious disease, and public health, specifically and only for the benefit of the child. It is based on when the vaccines are best tolerated and safest, and offer the greatest protection to the child.

Let’s review what went into the recommended schedule so that you can see the logic behind it.

DO MATERNAL ANTIBODIES PROTECT MY BABY?

Mothers pass protective antibodies across the placenta to their babies in the weeks before birth. These antibodies stay in the baby for about six months, and they offer helpful protection for the baby. However, they also have limitations. The antibodies that are given to the baby form “passive immunity,” meaning that those antibodies cannot be remade. When the baby makes her own antibodies, that is called “active immunity,” and it is more effective in fighting off disease. That is why vaccines still offer significant protection during this period.

ARE THERE VARYING RISKS OF INFECTION AT DIFFERENT AGES?

Some infections are much more severe the younger the infant is, such as pertussis, haemophilus, and pneumococcus infections. So, the most important time to protect the baby against them is early in infancy, and the longer a vaccine for these diseases is delayed, the less benefit an infant will receive from the vaccine.

With boosters at 2, 4, and 6 months, the baby’s active immunity builds up during this critical period as antibodies from the mother fade away, giving the baby a smooth transition to self-protection by the time they are gone. If, instead, vaccines did not start until 6 months of age, the baby’s active immunity would not be fully developed until months later. That would leave the baby with the least protection during the most critical period.

WHEN DO VACCINES PRODUCE THE BEST IMMUNE RESPONSE?

There is a big difference between when vaccines produce the strongest immune response versus when they offer the greatest benefit. In many cases, the immune response to a vaccine increases the older a child is. But it isn’t the strength of an immune response that matters most to the child’s health; it’s to what degree children do or don’t suffer any lasting health effects when all is said and done.

A perfectly adequate, modest immunity throughout infancy is far more desirable than suffering through the highest risk period with no immunity just so they can experience a stronger immune response to that vaccine at a later time—when there may be less or no risk from the disease anyway. Furthermore, a stronger immune response to a vaccine sometimes means stronger side effects.

For some vaccines, like measles, young babies do not respond well, so the vaccines are recommended only after 12 months of age. For other vaccines, such as pneumococcal vaccine, babies can respond well as early as 2 months of age (and babies that young are known to be at high risk), so vaccination is recommended to begin at that age.

The ideal situation you want to achieve is just enough immunity to stop a disease from doing harm, at the age when that disease causes the most harm. This can differ greatly depending on the vaccine, which is why different vaccines are at different places on the childhood schedule, all very precisely placed and timed to get
the best benefit with the fewest side effects. Because of this, altering the schedule will generally result in more side effects, less benefit, or both—you would be giving them at a time other than the time when their benefit-to-risk ratio is at its best.

SHOULD MY BABY GET MULTIPLE VACCINES AT ONE TIME OR SINGLE SHOTS AT MULTIPLE VISITS?

Once leaving the mother’s womb, which is a sterile environment, your child faces trillions of cells of bacteria, viruses, and yeast through the skin, nose, throat, intestines, and so on. Your baby keeps these organisms from causing serious disease by making immune responses to all the different cells—all at the same time. A child can respond to all of them simultaneously because of the billions of immunologic cells circulating through the body, each capable of doing its own work.

The 14 vaccines found on the childhood schedule contain a total of about 150 immunologic components—a tiny number on the immunologic scale. Out in the world, each bacterium alone can contain 2,000 to 6,000 immunological components, and your child processes many of them simultaneously. The entire vaccine schedule even all at once would be smaller than what your baby’s immune system manages every day.

Other considerations include the hassle for your family and the trauma for your child. It’s easy for doctors’ offices to do your shots on different days. But it’s most difficult on your family and your child. It means doubling the number of times your baby needs to get needle pokes. It also means scheduling more frequent doctor appointments and missing more time from work or school. And taking more time to complete a vaccination series obviously delays the protection that the vaccines offer. Perhaps these downsides would be worthwhile if we had evidence that giving vaccines on a more drawn-out schedule was better for babies. But we know that it isn’t.