Firstborn Children Are More Likely to Be Up to Date on Vaccinations

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Key Takeaways

  • A recent study found that among families, firstborn children are more likely to be up to date on their vaccinations than non-firstborn children.
  • The study suggests family size may partially, but not fully, explain these results.
  • Pediatricians say sticking to the Centers for Disease Control and Prevention's (CDC) recommended childhood vaccination schedule is critical for prevention.

If you have more than one child, you know what the constant juggle is like, and things sometimes fall through the cracks. But your child's vaccination schedule shouldn't be one of them. A recent study published by the American Academy of Pediatrics (AAP) suggests not all children actually receive their full doses according to the official Centers for Disease Control and Prevention (CDC) vaccine schedule. In fact, the order in which a child is born within a family may actually affect whether they are fully vaccinated.

Most children start receiving their vaccinations from the time they are babies, and studies have shown vaccines are among the most effective and safest public health interventions available to prevent serious disease and death. According to the CDC, children should be vaccinated for the following diseases by the time they’re 6 years old:

  • Hepatitis A and hepatitis B
  • Rotavirus
  • Diphtheria, tetanus, and acellular pertussis
  • Haemophilus influenzae type B
  • Polio
  • Pneumococcal disease
  • Measles, mumps, and rubella
  • Varicella
  • Influenza

After adjusting for sociodemographic variables, researchers in this new study found first-born children were significantly more likely to be up to date for all eight individual vaccines and all four vaccine series. The study also suggested family size may partially explain the results.

Why Birth Order Is Affecting Immunizations

The study does say more research is needed to determine why birth order affects immunizations this much. But researchers did provide some suggestions as to why it plays such a big role.

Family size may be a factor, with the amount of available resources and level of parental involvement impacting latter-born children. Parents could feel a sense of urgency when it comes to their firstborn children, considering they are getting used to their new roles as caregivers. In the case of multiple children, parents may need to schedule time off to make appointments for the vaccinations. Instead, they might try to pair all their children’s appointments together, which could lead to schedules being missed and shots being delayed.

Jessica Madden, MD, a medical director at Aeropumps, also believes much of the delay in vaccinations of later-born children can be due to the recent pandemic. “It was difficult for many children to be seen by their pediatricians for well visits in a timely manner due to quarantines, staffing shortages, and temporary clinic closures. Plus, many doctors retired early or left the workforce,” she says.

“As a result, many newborns and infants missed their well child visits where they would have received their vaccines," Dr. Madden adds. "Anecdotally, another reason for the decreased rates seems to be due to parents having more ‘vaccine hesitancy’ after receiving so many mixed messages with regard to the need for [and efficacy of] the COVID-19 vaccines [and others] through the media in the past few years.”

Why It's Important to Keep Your Child's Vaccine Schedule

While there are several reasons why parents might delay their children’s vaccine schedule, pediatricians all unequivocally agree that keeping children on schedule is of the utmost importance in order to prevent disease. In fact, research has indicated that in 2019, routine childhood vaccines prevented a whopping 24 million diseases—suggesting how effective they can truly be.

“The number one reason to keep to the CDC’s recommended vaccine schedule is to prevent your children from getting ill and developing complications (or even dying) from a serious bacterial or viral infection,” stresses Dr. Madden. “The reason that infants get three rounds of vaccines (at two, four, and six months) is because the passive immunity that they receive from their moms in-utero (mothers’ antibodies crossing the placenta to protect babies) wears off by about six months after birth.”

Jessica Madden

The number one reason to keep to the CDC’s recommended vaccine schedule is to prevent your children from getting ill and developing complications (or even dying) from a serious bacterial or viral infection.

— Jessica Madden

According to Dr. Madden, unimmunized infants are particularly susceptible to pertussis (whooping cough), Haemophilus influenzae type B, and pneumococcal infections due to this loss of immunity from their mothers.

“These infections can all cause respiratory distress, meningitis, and sepsis, and they were a large reason why the infant mortality in the U.S. was so high prior to routine immunizations,” she says. “So, keeping your child up-to-date on vaccine schedules is absolutely key.”

Who Sets Children's Vaccination Schedule?

The CDC sets the vaccination schedule for children based on current medical data. Public health experts routinely review available information on newly licensed and existing vaccines. They meet about three times a year to discuss vaccine recommendations. These vaccine experts, scientists, doctors, and public health professionals form the CDC's Advisory Committee on Immunization Practices (ACIP).

The ACIP also considers a lot of factors when reviewing data. They include safety and effectiveness, severity of the disease, the number of people people who may contract the disease if there is no vaccine, and how well the vaccine helps produce immunity.

The final vaccine recommendations include the number of doses, timing between doses, the age when infants and children should be vaccinated, as well as precautions and who should not receive the vaccine.

Once the ACIP provides its recommendations, the CDC sets the immunization schedules. The childhood and adolescent schedules are also approved by the American Academy of Pediatrics (AAP), the American Academy of Family Physicians (AAFP), and the American College of Obstetricians and Gynecologists. 

How Does the Flu Shot Fit in My Child's Vaccination Schedule?

During the 2021-2022 flu season, only 55% of children were vaccinated to protect against influenza. Coverage levels were also 8.1% points lower for Black children compared with white children, according to the CDC. However, the flu shot is critical, according to board-certified physician Preeti Parikh, MD. 

“The flu shot can protect you from getting sick, and if you’ve had the flu shot and still get the flu, the vaccine can help you have a milder case. It may even protect you from ending up in the hospital or ICU,” she says.

It's important to know that children can get sick with influenza very easily during flu season. "Most of the time, flu symptoms can be handled at home without specific treatment," Dr. Parikh points out. "However, there is always a risk of the flu becoming dangerous. The best way to keep kids from getting the flu is to make sure they are vaccinated.” This is especially true for children under 2 years old, who are at high risk of getting very sick with the flu.

“Infants can receive their first flu shot when they are 6 months old, and this is typically given at the same time as the other 6-month vaccines,” adds Dr. Madden. “The first time an infant receives the flu vaccine, they need to have it repeated one month later to have full immunity and protection from the flu. After this, the flu shot is given annually.”

How Does the COVID-19 Vaccine Fit in My Child's Schedule?

You may be wondering how the COVID-19 vaccine fits into all of this. The CDC has approved COVID-19 vaccines and boosters for children as young as 6 months old.

“There are two COVID vaccines: Pfizer, which is available in three doses for 6-month-olds to 5-year-olds,” says Dr. Parikh. “After the third dose, they are considered immunized. The second vaccine, Moderna, is available in two doses for 6-month-olds to 5-year-olds...One is considered fully vaccinated after the second dose.”

The COVID-19 vaccine doesn't affect the course of a child's vaccine schedule. “Infants and children who are at least 6 months old can receive the COVID-19 vaccine at any visit, and also at the same time as their other vaccines,” says Dr. Madden.

What This Means For You

A new study shows later-born children aren’t as up-to-date on their vaccines as first-born children. Parents may miss or delay vaccines due to time constraints or a lack of urgency, and the recent COVID-19 pandemic may have also played a role. However, pediatricians say keeping children up to date on vaccines is essential for preventing serious illness down the line. If time is an issue, parents can pair some vaccines together at the same time, such as the flu and COVID-19 vaccines. If you're hesitant or have questions about your child's vaccine schedule, make sure you speak with their pediatrician.

11 Sources
Verywell Family 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.
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By Nikhita Mahtani
Nikhita Mahtani is a contributing writer with extensive experience in parenting, health, and wellness. She primarily uses her contacts in the mental health and medical industry to help readers deal with stress and burnout, prejudices or racial bias—especially in the parenting space, and the mind-body connection.