How Vaccine Schedules Are Determined

Doctor applying bandage after giving vaccine

adamkaz / Getty Images

As researchers find new and safer ways to combat dangerous diseases, the U.S. schedule of vaccines has grown substantially. Today, fully vaccinated kids and teens are protected from 16 diseases—far more than their parents or grandparents.

While most parents have embraced these changes, some worry about the increasing number and frequency of vaccines children get during the first few years of life and wonder whether or not the schedule is safe to follow.

It's natural to be cautious. With access to so much conflicting information and heartbreaking stories on social media, it can be difficult for parents to know whose recommendations to trust—especially when it comes to health. That's why it's so crucial to gain a better understanding of how the routine vaccination schedule is developed, and why it's widely considered to be the safest and most effective way to protect children from potentially serious infections.

Who Decides the Childhood Vaccination Schedule?

While the Food and Drug Administration (FDA) decides if vaccines can be sold in the U.S., it’s the Advisory Committee on Immunization Practices (ACIP) that makes recommendations on what vaccines should be given and when. These recommendations are later adopted by the Centers for Disease Control and Prevention (CDC) and the American Academy of Pediatrics (AAP) and used by medical teams all over the country to vaccinate patients.

The ACIP is a voluntary group of public health and medical experts consisting of:

  • A group of 15 voting members who are chosen by the Secretary of the U.S. Department of Health and Human Services after an application and nomination process. Of this group, 14 have extensive experience in medical or public health fields directly related to vaccination, such as researchers, medical doctors, and infectious diseases specialists. At least one is a consumer representative that can offer a perspective on the less direct impacts of the vaccination schedule, such as how changes to the schedule could affect communities.
  • Representatives from dozens of professional organizations like the AAP and the American Academy of Family Physicians. These members can offer insight and perspective on potential recommendations or changes to the schedule, but they don't get to vote on them.

To protect against conflicts of interest, applicants with current ties to vaccine manufacturers are denied, and researchers who are active in studying certain vaccines can't participate in votes related to the vaccine they're studying or vaccines made by companies funding their research.

How Often Is the Vaccination Schedule Updated?

The ACIP meets three times a year to go over all currently available research on issues related to vaccines and update the schedule accordingly. To make the process as transparent as possible, the committee posts their meeting minutes and timed agendas up on the CDC's website, and all ACIP meetings are open to the public and broadcast live via a webcast.

Between meetings, members work on small work groups that focus on specific vaccines and diseases. These groups pore over all the latest research—including information on vaccines yet to be approved by the FDA—in order to brief the whole committee. New vaccines are discussed multiple times, with continual updates from the work groups, before they are even considered to be added to the vaccination schedule.

When the voting members vote, they take into consideration a wide variety of factors, including:

  • Is the vaccine safe and effective when given at specific ages and with other vaccines given at the same time?
  • Does the vaccine protect against a serious and potentially life-threatening disease or condition?
  • Will a lot of children get the disease if they don't get the vaccine?
  • How practical would this recommendation be for patients and medical practitioners to follow?

After all of these questions and more have been thoroughly discussed and debated, and the public has been given an opportunity to share their thoughts during the meetings, the committee votes to include, remove, or modify certain recommendations and a new, revised schedule is published at the beginning of each calendar year.

It should be noted that this schedule isn't to tell parents what vaccines are required for school. That list is set up by each individual state government. Its main purpose is to guide doctors, parents, and caregivers on what vaccines should be routinely given based on a number of factors.

Is the Yearly Vaccination Schedule Set in Stone?

The schedule resulting from the processes outlined above is the safest and most comprehensive way to protect kids from diseases, based on the most current research.

Once recommendations are made and the schedule is published, the scrutiny doesn't stop. The ACIP makes the schedule based on all the data they have at the moment, but new information is always being collected. If at any time research is pointing to a vaccine not being as safe or effective as previously thought, or if doses need to be added or spaced differently, the schedule is adapted.

For example, in 2016 the ACIP voted to no longer recommend the nasal spray version of the flu vaccine. When it was first released, early data on the vaccine showed that it was as effective—if not more so—than the traditional flu shot. But new research from 2013-2015 showed it to be substantially less effective than previously believed. In light of the new information, the ACIP dropped its recommendation for the upcoming flu season, and instead recommended that everyone over six months get the traditional, injected flu shot.

The ACIP's job is to carefully weigh risks versus benefits, and when the benefits of the nasal spray flu vaccine no longer outweighed the risks associated with it, they changed the schedule to reflect that.

Does the Schedule Apply Equally to Everyone?

While the immunization schedule is designed to be broadly applied to all children of a certain age, there are some children that might need to follow an adjusted schedule due to medical conditions or certain risk factors. Children who are transplant recipients, for example, often are unable to receive live vaccines, like those against measles or mumps, because their body's defenses are weakened. Those who are at a greater-than-average risk for diseases that cause meningitis might need to be vaccinated at an earlier age than their peers.

The ACIP takes those kids into consideration and has special footnotes within the schedule to provide guidance for medical professionals on who should slow down, speed up, add or subtract certain vaccines and when. For the overwhelming majority of children and adolescents, however, sticking to the routinely recommended schedule is the best way to go.

Is It Harmful to Follow a Different Schedule?

Even when parents value vaccines as an important step to protecting their children's health, they can still be hesitant to follow the recommended schedule. Some, instead, decide to delay or forgo some vaccines or opt to "space out" doses so that their children only receive one at a time. In doing so, they hope to minimize the risks associated with vaccination, but following these kinds of alternative schedules could actually increase risks.

Not only does spacing out vaccines leave kids vulnerable to infections for longer than necessary—putting them at risk of exposure to diseases like measles and whooping cough while they wait to be vaccinated—but they also require more frequent visits to a doctor's office where they could catch other diseases as well.

But perhaps most importantly, the recommended childhood vaccination schedule made by the ACIP is designed to protect kids as early—but also as safely—as possible. Giving vaccines in different combinations or at different intervals could make them less effective, or make side effects more likely. We don't know. While we routinely study the safety and effectiveness of the ACIP recommendations, we don't have the same data for customized schedules.

Modifying the schedule based on individual beliefs or preferences doesn't eliminate risks—it simply changes what risks parents are taking.

Vaccine Schedules Differ From Country to Country—and That's OK

While the U.S. has a similar immunization schedule to the one used by the United Kingdom or Australia, the timing and types of vaccines differ. And that's because countries differ. It is up to each nation to determine their own vaccination schedule based on its own analyses of benefits versus risks. Factors like how common a disease is and how patients gain access to vaccines and medical treatment can vary widely from country to country, and these considerations are critical when debating when vaccines should be given.

The World Health Organization assists in this process by offering guidance on recommended vaccination schedules, though it should be noted these schedules are meant to be used as a reference by national vaccination programs, not patients or physicians.

Vaccines Doctor Discussion Guide

Get our printable guide for your next doctor's appointment to help you ask the right questions.

Doctor Discussion Guide Child
Was this page helpful?
Article Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Centers for Disease Control and Prevention. Recommended vaccines by age. Updated November 22, 2016.

  2. Centers for Disease Control and Prevention. Advisory Committee on Immunization Practices (ACIP). Updated December 4, 2019.

  3. Centers for Disease Control and Prevention. Prevention and control of seasonal influenza with vaccines recommendations of the Advisory Committee on Immunization Practices — United States, 2016–17 Influenza Season. Updated August 26, 2016.

  4. KidsHealth. Common questions about immunizations. Updated March 2019.

  5. World Health Organization. WHO recommendations for routine immunization - summary tables. Updated April 26, 2019.