Analysis of health outcomes in vaccinated and unvaccinated children: Developmental delays, asthma, ear infections and gastrointestinal disorders

SAGE Open Medicine

Volume 8: 1 –11

© The Author(s) 2020

Article reuse guidelines:

DOI: 10.1177/2050312120925344

Brian S Hooker1 and Neil Z Miller2


Objective: The aim of this study was to compare the health of vaccinated versus unvaccinated pediatric populations.

Methods: Using data from three medical practices in the United States with children born between November 2005 and June 2015, vaccinated children were compared to unvaccinated children during the first year of life for later incidence of developmental delays, asthma, ear infections and gastrointestinal disorders. All diagnoses utilized International Classification of Diseases–9 and International Classification of Diseases–10 codes through medical chart review. Subjects were a minimum of 3 years of age, stratified based on medical practice, year of birth and gender and compared using a logistic regression model.Results: Vaccination before 1 year of age was associated with increased odds of developmental delays (OR = 2.18, 95% CI 1.47–3.24), asthma (OR = 4.49, 95% CI 2.04–9.88) and ear infections (OR = 2.13, 95% CI 1.63–2.78). In a quartile analysis, subjects were grouped by number of vaccine doses received in the first year of life. Higher odds ratios were observed in Quartiles 3 and 4 (where more vaccine doses were received) for all four health conditions considered, as compared to Quartile 1. In a temporal analysis, developmental delays showed a linear increase as the age cut-offs increased from 6 to 12 to 18 to 24 months of age (ORs = 1.95, 2.18, 2.92 and 3.51, respectively). Slightly higher ORs were also observed for all four health conditions when time permitted for a diagnosis was extended from ⩾ 3 years of age to ⩾ 5 years of age.Conclusion: In this study, which only allowed for the calculation of unadjusted observational associations, higher ORs were observed within the vaccinated versus unvaccinated group for developmental delays, asthma and ear infections. Further study is necessary to understand the full spectrum of health effects associated with childhood vaccination.


Vaccination is considered to be one of the most important advances in modern public health.1

Currently, children between birth and 6 years of age receive up to 36 vaccine doses to protect against 14 different diseases, according to the Centers for Disease Control and Prevention’s (CDC) recom-mended schedule.2 By ages 1 and 2 years, the CDC recom-mends approximately 21 and 28 such vaccination doses, respectively.

The number of vaccine doses received by infants and children has increased most notably since the early 1990s, when the hepatitis B and Haemophilus influenzae type B vaccines were introduced. Currently, children in the United States are vaccinated for hepatitis A and B, Haemophilus influenzae type B, diphtheria, pertussis, tetanus, polio, measles, mumps, rubella, rotavirus, pneumococcal pneumo-nia, influenza and varicella.

Although short-term clinical testing is completed on individual vaccines (with limited longer-term follow-up for specific vaccine adverse events) prior to approval by the US Food and Drug Administration (FDA), the health outcomes related to these vaccines and the vaccination schedule as a whole are largely unknown.3 For instance, Kuter et al.4detailed 23 different post-licensing trials conducted on the measles, mumps and rubella (MMR)-II vaccine and in no instance were the patients followed for more than 42 days post-vaccination.

In 2011, the Institute of Medicine (IOM)5published the report “Adverse Effects of Vaccines: Evidence and Causality” where the relationships between specific vaccines and different adverse health effects were consid-ered. Based on the current scientific literature, the IOM committee found inadequate evidence to accept or reject a causal relationship between 135 of 158 relationships between vaccines and adverse events. Among the remaining 23 adverse events, 18 were found to be associated with vac-cination and 5 were not.The medical community does in general acknowledge that vaccination is not without health risks, including death.6

However, it is widely purported that these side effects or “adverse events” are extremely rare and justified compared to the overall benefit of vaccination.7 There have been very few studies reported where health effects of the US infant and childhood vaccination schedule have been assessed. This is in part based on ethical concerns of withholding vac-cination from an unvaccinated control group within such a study.8 Indeed, this precludes the use of double-blinded pla-cebo studies on vaccine health effects, and even in clinical trials an earlier version of the same vaccine is often used as the placebo control for the newly tested vaccine.

One study, published by Mawson et al.,3 was based on a convenience sample of homeschooled children where a sig-nificant portion of the sample (39%) was unvaccinated. In this small sample, vaccinated children showed higher odds of being diagnosed with pneumonia, otitis media, allergies and neurodevelopmental disorders. In addition, preterm birth coupled with vaccination significantly increased the odds of a neurodevelopmental disorder diagnosis. This study was unique in the inclusion of entirely unvaccinated populations to provide a comparison to partially vaccinated and fully vaccinated children. However, the risk of bias is high when comparing vaccinated versus unvaccinated children. Also, health outcomes were based on parental survey, not con-firmed by medical chart review, and may be subject to recall bias, and the small size of the sample (666 patients) made it difficult to analyze for rare disorders.

Between 2001 and 2004, the IOM9 Immunization Safety Review Committee rejected a relationship between multiple vaccinations and sudden infant death syndrome (SIDS) but could not rule out a relationship with other types of “sudden unexpected infant death.” This included the neonatal hepati-tis B vaccine as well as the diphtheria and tetanus toxoids and whole-cell pertussis (DTwP) vaccine, which was strongly associated with anaphylaxis but is no longer given in the United States. A relationship between multiple vac-cines and type 1 diabetes was ruled out, but evidence was inadequate to accept or reject a relationship with asthma.10

In addition, the committee rejected a relationship between multiple vaccines and increased “heterologous” infections, such as bacterial infections unrelated to vaccine-preventable diseases, although recent studies have provided evidence of both beneficial and detrimental non-specific effects associ-ated with several vaccines.11–13 The remainder of the IOM Immunization Safety Review Committee focused on single types of vaccines and specific adverse events as recom-mended by the CDC who commissioned these studies.

In the study presented here, children from three different pediatric medical practices in the United States were used as a convenience sample for comparing patients vaccinated and unvaccinated within the first year of life.

Vaccination records were based on data within each practice’s electronic medical records (EMRs) system. Four different diagnoses were eval-uated, along with one control diagnosis presumed not to cor-relate with vaccination status.

To allow time for a diagnosis to be made, children were a minimum of 3 years of age for each analysis completed (except for Table 9, where the mini-mum age was extended)

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