Maternal and Newborn Hospital Outcomes of Perinatal SARS-CoV-2 Infection: A National Registry

Successes and Lessons Learned in Responding to the Needs of Pediatricians, Children, and Families During the COVID-19 Pandemic

The coronavirus disease 2019 pandemic has presented tremendous challenges to the United States health care system, as well as to individual physicians, communities, and families. Throughout the pandemic, the American Academy of Pediatrics (AAP) has striven to elevate the needs of infants, children, and adolescents, as well as the pediatricians who care for this population. Historically, these communities have often been overlooked and deprioritized in health care systems, and these deficits persisted into the pandemic. To fill this gap, the AAP took on an essential role in leading the national response for pediatrics. This article details the AAP pandemic response and includes the perspectives of multiple AAP leaders involved in the response and details on Academy advocacy with high-level staff and officials at federal agencies and the executive branch. The AAP provided initial guidance to pediatricians that predated the World Health Organization's declaration of a public health emergency. The Academy then developed entirely new approaches to meet the unprecedented needs of its practicing members and families by providing timely, rigorous information endorsed by pediatric experts. When coronavirus disease 2019 vaccines were developed, the AAP strongly advised the inclusion of those younger than 18 years in vaccine trials and advocated for equitable distribution plans. The AAP provided its members with strategies for combating misinformation. The Academy was at the forefront of advocating for the safe return to in-person schooling, recognizing that social isolation was contributing to the growing mental health crisis among youth. In 2021, the AAP, the American Academy of Child and Adolescent Psychiatry, and the Children's Hospital Association declared a national emergency in child and adolescent mental health. In addition, the AAP implemented educational and training opportunities for clinicians and developed resources for youth and their families. After the end of the public health emergency, AAP members continue to use innovations and efficiencies developed as part of their pandemic response. The successes of the AAP pandemic response, alongside lessons learned, help define an important model for responding to future pandemics and public health emergencies in ways that support children, families, and the pediatric workforce.

Maternal and neonatal outcomes associated with illness severity of maternal COVID-19

BACKGROUND

Several reports demonstrated that perinatal SARS-CoV-2 has significant impact on maternal and neonatal health outcomes. However, the relationship between severity of maternal illness with outcomes remains less clear.

METHODS

This is a single-center retrospective cohort study of mother/infant dyads with positive maternal test for SARS-CoV-2 between 14 days prior and 3 days after delivery from 3/30/2020 to 12/28/2021.

RESULTS

Among 538 mothers, those with moderate/severe/critical illness were more likely to undergo induction, receive oxygen, mechanical ventilation or ECMO. Mortality was significantly higher among the mothers with severe illness than asymptomatic and those with mild illness (6% vs 0% and 0%, respectively, P < 0.05). Neonates born to mothers with moderate/severe/critical illness were more likely to be preterm with lower birth weight, and to be admitted to the NICU (P < 0.05) but not to be small for gestational age. Mild maternal illness was only associated with NICU admission for isolation precaution and decreased rate of breastfeeding.

CONCLUSIONS

Maternal illness severity was significantly associated with prematurity and several adverse maternal and neonatal outcomes.

Nationwide Analysis of the Outcomes and Mortality of Hospitalized Infants with Concomitant Diagnosis of COVID-19

OBJECTIVE

 Coronavirus disease 2019 (COVID-19) generally causes milder illness in the pediatric population. However, infants represent a higher-risk population with evolving symptomatology and severity. There is a paucity of large population-based data on the impact of COVID-19 on hospitalized infants.

STUDY DESIGN

 In this large cohort study, the National Inpatient Sample database was queried for all infant hospital admissions between January and December 2020 in the United States, with and without a diagnosis of COVID-19 based on ICD-10-CM U07. The mortality and morbidity of infants with and without COVID-19 were evaluated. Parent-reported race and outcomes were also analyzed.

RESULTS

 A weighted total of 3,754,236 infants who were hospitalized were identified, of which 4,265 patients (0.11%) had a concomitant diagnosis of COVID-19. Infants with COVID-19 had similar mortality and extracorporeal membrane oxygenation utilization. Infants with concomitant COVID-19 had a higher rate of respiratory failure, congestive heart failure, acute kidney injury, and coagulopathy. Compared with Caucasian infants and Asian infants, Hispanic and African American infants were more likely to have COVID-19 hospital admissions than hospitalizations without COVID-19 diagnosis. Patients with lower median household income represented the majority of the COVID-19 hospitalization. The infants with COVID-19 were more likely to have Medicaid or Medicare insurance and less likely to have private insurance.

CONCLUSION

 In this large cohort of hospitalized infants with COVID-19, the infection was associated with complications, including respiratory failure and endotracheal intubations but not associated with a higher risk for mortality. Infants from racial minorities and lower socioeconomic strata carry the highest burden of COVID-19 infection.

KEY POINTS

· Infants with COVID-19 represent a higher-risk group with evolving symptomatology and severity.. · Infants with COVID-19 had similar mortality rates and extracorporeal membrane oxygenation utilization as those without COVID-19.. · Racial minorities and lower socioeconomic strata carry the highest burden of COVID-19 infection..

Prevalence of SARS-CoV-2 in newborns born to SARS-CoV-2-positive mothers at 2 weeks of life

Introduction

Limited evidence exists on management recommendations for neonates born to SARS-CoV-2-positive mothers. This study looked at transmission risk of neonates presenting for primary care in a large regional health system within New York during the early months of the COVID-19 pandemic.

Methods

This was a prospective, observational study of newborns born to SARS-CoV-2-positive mothers presenting at any of the 19 Northwell Health-Cohen Children's Medical Center primary care practices who underwent another oropharyngeal/nasopharyngeal swab for detection of SARS-CoV-2 by day of life (DOL) 14.

Results

Among 293 newborns born to SARS-CoV-2-positive mothers who were negative at birth, 222 were retested at DOL 14, corresponding to times with different predominant strains. Of these, seven tested positive but had no symptoms.

Conclusion

The overall low transmission rates and absence of symptomatic infection support the safety of direct breastfeeding after hospital discharge with appropriate hand and breast hygiene.

Characteristics and outcomes of neonates hospitalised with SARS-CoV-2 infection in the UK by variant: a prospective national cohort study

OBJECTIVE

Neonatal infection with wildtype SARS-CoV-2 is rare and good outcomes predominate. We investigated neonatal outcomes using national population-level data to describe the impact of different SARS-CoV-2 variants.

DESIGN

Prospective population-based cohort study.

SETTING

Neonatal, paediatric and paediatric intensive care inpatient care settings in the UK.

PATIENTS

Neonates (first 28 days after birth) with confirmed SARS-CoV-2 infection who received inpatient care, March 2020 to April 2022. Neonates were identified through active national surveillance with linkage to national SARS-CoV-2 testing data, routinely recorded neonatal data, paediatric intensive care data and obstetric and perinatal mortality surveillance data.

OUTCOMES

Presenting signs, clinical course, severe disease requiring respiratory support are presented by the dominant SARS-CoV-2 variant in circulation at the time.

RESULTS

344 neonates with SARS-CoV-2 infection received inpatient care; breakdown by dominant variant: 146 wildtype, 123 alpha, 57 delta and 18 omicron. Overall, 44.7% (153/342) neonates required respiratory support; short-term outcomes were good with 93.6% (322/344) of neonates discharged home. Eleven neonates died: seven unrelated to SARS-CoV-2 infection, four were attributed to neonatal SARS-CoV-2 infection (case fatality 4/344, 1.2% 95% CI 0.3% to 3.0%) of which three were born preterm due to maternal COVID-19. More neonates were born very preterm (23/54) and required invasive ventilation (27/57) when delta variant was predominant, and all four SARS-CoV-2-related deaths occurred in this period.

CONCLUSIONS

Inpatient care for neonates with SARS-CoV-2 was uncommon. Although rare, severe neonatal illness was more common during the delta variant period, potentially reflecting more severe maternal disease and associated preterm birth.

TRIAL REGISTRATION NUMBER

ISRCTN60033461.

Prenatal Infection by Respiratory Viruses Is Associated with Immunoinflammatory Responses in the Fetus

Rationale: Respiratory viral infections can be transmitted from pregnant women to their offspring, but frequency, mechanisms, and postnatal outcomes remain unclear. Objectives: The aims of this prospective cohort study were to compare the frequencies of transplacental transmission of respiratory syncytial virus (RSV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), analyze the concentrations of inflammatory mediators in maternal and fetal blood, and assess clinical consequences. Methods: We recruited pregnant women who developed upper respiratory infections or tested positive for SARS-CoV-2. Maternal and cord blood samples were collected at delivery. Study questionnaires and electronic medical records were used to document demographic and medical information. Measurements and Main Results: From October 2020 to June 2022, droplet digital PCR was used to test blood mononuclear cells from 103 mother-baby dyads. Twice more newborns in our sample were vertically infected with RSV compared with SARS-CoV-2 (25.2% [26 of 103] vs. 11.9% [12 of 101]; P = 0.019). Multiplex ELISA measured significantly increased concentrations of several inflammatory cytokines and chemokines in maternal and cord blood from newborns, with evidence of viral exposure in utero compared with control dyads. Prenatal infection was associated with significantly lower birth weight and postnatal weight growth. Conclusions: Data suggest a higher frequency of vertical transmission for RSV than SARS-CoV-2. Intrauterine exposure is associated with fetal inflammation driven by soluble inflammatory mediators, with expression profiles dependent on the virus type and affecting the rate of viral transmission. Virus-induced inflammation may have pathological consequences already in the first days of life, as shown by its effects on birth weight and postnatal weight growth.

SARS-CoV-2 perinatal transmission and neonatal outcomes across four different waves of COVID-19 pandemic: A nationwide prospective cohort study from the Italian Society of Neonatology

OBJECTIVES

To describe how SARS-CoV-2 infection at the time of delivery affected maternal and neonatal outcomes across four major waves of the COVID-19 pandemic in Italy.

METHODS

This is a large, prospective, nationwide cohort study collecting maternal and neonatal data in case of maternal peripartum SARS-CoV-2 infection between February 2020 and March 2022. Data were stratified across the four observed pandemic waves.

RESULTS

Among 5201 COVID-19-positive mothers, the risk of being symptomatic at delivery was significantly higher in the first and third waves (20.8-20.8%) than in the second and fourth (13.2-12.2%). Among their 5284 neonates, the risk of prematurity (gestational age <37 weeks) was significantly higher in the first and third waves (15.6-12.5%). The risk of intrauterine transmission was always very low, while the risk of postnatal transmission during rooming-in was higher and peaked at 4.5% during the fourth wave. A total of 80% of positive neonates were asymptomatic.

CONCLUSION

The risk of adverse maternal and neonatal outcomes was significantly higher during the first and third waves, dominated by unsequenced variants and the Delta variant, respectively. Postnatal transmission accounted for most neonatal infections and was more frequent during the Omicron period. However, the paucity of symptoms in infected neonates should lead us not to separate the dyad.

Vertical transmission of SARS-CoV-2 - data from the German COVID-19 related obstetric and neonatal outcome study (CRONOS)

OBJECTIVES

We aimed to determine the frequency of SARS-CoV-2 positivity in newborns born to mothers with peripartum SARS-CoV-2 infection in a German cohort, to identify potential risk factors associated with neonatal SARS-CoV-2 infection, and to present short-term outcomes of newborns with vertical transmission of SARS-CoV-2.

METHODS

Data on women with SARS-CoV-2 infection occurring anytime during their pregnancy was gathered prospectively within the CRONOS registry. From April 2020 to February 2023 a total of 8,540 women had been registered. The timing and the probability of mother-to-child transmission in neonates born to women with perinatal SARS-CoV-2 infection were classified using the WHO classification system. The severity of maternal infection, maternal vaccination status, type of dominant virus, and perinatal outcome parameters were analyzed as potential risk factors for neonatal SARS-CoV-2 infection.

RESULTS

6.3 % resp. 42.9 % of tested newborns and stillbirths were SARS-CoV-2 positive. 2.1 % of newborns with confirmed and possible SARS-CoV-2 infection were identified. Severe maternal COVID-19 (odds ratio 4.4, 95 % confidence interval 1.8-11.1) and maternal infection with the Delta virus (OR 3.2, 1.4-7.7) were associated with neonatal SARS-CoV-2 infection. Newborns with a confirmed or possible infection were significantly more often admitted to the NICU (65.2 % neonatal infection vs. 27.5 % non, p<0.001).

CONCLUSIONS

The rate of neonatal SARS-CoV-2 positivity was higher in our cohort than previously reported, neonatal SARS-CoV-2 infections were rare. Our data emphasizes confirmative testing should be performed in newborns of SARS-CoV-2 infected mothers to identify neonatal SARS-CoV-2 infection as an underlying pathology leading to NICU admission.

COVID-19, Pregnancy, and Diabetes Mellitus

During the severe acute respiratory distress virus coronavirus type 2 (SARS-CoV-2) pandemic, many women were infected during their pregnancies. The SARS-CoV-2-induced coronavirus disease 19 (COVID-19) has an impact on maternal health and pregnancy outcomes; peripartum and perinatal morbidity and mortality are increased. Pregnancy is considered a risk factor for severe COVID-19 course. Additional risk factors during pregnancy are diabetes mellitus, gestational diabetes mellitus (GDM), and obesity. Systemic inflammation can lead to severe metabolic dysregulation with ketoacidosis. The endocrine pancreas is a target organ for SARS-CoV-2 and the fetal risk depends on inflammation of the placenta. Up to now there is no evidence that SARS-CoV-2 infection during pregnancy leads to permanent diabetes in mothers or their offspring via triggering autoimmunity or beta cell destruction. The frequently observed increased prevalence of GDM compared to the years before the pandemic is most likely due to changed lifestyle during lockdown. Furthermore, severe COVID-19 may be associated with the development of GDM due to worsening of glucose tolerance. Vaccination with a mRNA vaccine is safe and highly effective to prevent infection and to reduce hospitalization. Registries support offering evidence-based recommendations on vaccination for pregnant women. Even with the current omicron virus variant, there are increased risks for symptomatic and unvaccinated pregnant women.

Adverse perinatal outcomes in gestational diabetes mellitus with and without SARS-CoV-2 infection during pregnancy: results from two nationwide registries in Germany

INTRODUCTION

Pregnancy is a known independent risk factor for a severe course of COVID-19. The relationship of SARS-CoV-2 infection and gestational diabetes mellitus (GDM) on neonatal outcomes is unclear. Our aim was to determine if SARS-CoV-2 infection represents an independent risk factor for adverse perinatal outcomes in pregnancy with GDM.

RESEARCH DESIGN AND METHODS

We compared data from two German registries including pregnant women with GDM, established during the SARS-CoV-2 pandemic (COVID-19-Related Obstetric and Neonatal Outcome Study (CRONOS), a multicenter prospective observational study) and already existing before the pandemic (German registry of pregnant women with GDM; GestDiab). In total, 409 participants with GDM and SARS-CoV-2 infection and 4598 participants with GDM, registered 2018-2019, were eligible for analyses. The primary fetal and neonatal outcomes were defined as: (1) combined: admission to neonatal intensive care unit, stillbirth, and/or neonatal death, and (2) preterm birth before 37+0 weeks of gestation. Large and small for gestational age, maternal insulin therapy, birth weight >4500 g and cesarean delivery were considered as secondary outcomes.

RESULTS

Women with SARS-CoV-2 infection were younger (32 vs 33 years) and had a higher median body mass index (28 vs 27 kg/m²). In CRONOS, more neonates developed the primary outcome (adjusted OR (aOR) 1.48, 95% CI 1.11 to 1.97) and were born preterm (aOR 1.50, 95% CI 1.07 to 2.10). Fasting glucose was higher in women in CRONOS versus GestDiab (5.4 vs 5.3 mmol/L) considering each 0.1 mmol/L increase was independently associated with a 5% higher risk of preterm birth among women in CRONOS only (aOR 1.05, 95% CI 1.01 to 1.09).

CONCLUSIONS

GDM with SARS-CoV-2 infection in pregnancy is associated with an increased risk of adverse fetal and neonatal outcomes as compared with GDM without SARS-CoV-2 infection.

Trends in COVID-19 diagnoses and outcomes in infants hospitalized in the neonatal intensive care unit

OBJECTIVE

Characterize the prevalence of coronavirus disease 2019 (COVID-19) diagnosis among mothers with infants hospitalized in 294 neonatal intensive care units (NICUs), and demographics and outcomes of infants with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) exposure in utero.

STUDY DESIGN

Cohort study of infants discharged from NICUs 01/2020-09/2021. We defined groups based on infant diagnosis, infant testing, and maternal SARS-CoV-2 infection status. We compared demographics, clinical characteristics, and outcomes.

RESULTS

Of 150,924 infants, 94% had no COVID-related diagnosis or test; 247 (0.2%) infants tested positive for COVID-19 and were more likely to require mechanical ventilation. Infants with unknown maternal status and negative testing were more commonly premature, outborn, and had longer hospitalizations.

CONCLUSION

In this large cohort of hospitalized infants, most had no known exposure to COVID-19. Adverse outcomes and mortality were rare. Further studies are needed to evaluate the long-term effects of COVID-19 in this population.

Mechanisms of SARS-CoV-2 Placental Transmission

The widespread occurrence of SARS-CoV-2 infections and the diverse range of symptoms have placed significant strain on healthcare systems worldwide. Pregnancy has also been affected by COVID-19, with an increased risk of complications and unfavorable outcomes for expectant mothers. Multiple studies indicate that SARS-CoV-2 can infiltrate the placenta, breach its protective barrier, and infect the fetus. Although the precise mechanisms of intrauterine transmission remain unclear, factors such as perinatal infection, macrophages, sexual intercourse, and the virus' interaction with host angiotensin-converting enzyme 2 (ACE2) and neuropilin-1 (NRP-1) proteins appear to play a role in this process. The integrity of the placental barrier fluctuates throughout pregnancy and appears to influence the likelihood of fetal transmission. The expression of placental cell receptors, like ACE2, changes during pregnancy and in response to placental damage. However, due to the consistent presence of others, such as NRP-1, SARS-CoV-2 may potentially enter the fetus at different stages of pregnancy. NRP-1 is also found in macrophages, implicating maternal macrophages and Hofbauer cells as potential routes for viral transmission. Our current understanding of SARS-CoV-2's vertical transmission pathways remains limited. Some researchers question the ACE2-associated transmission model due to the relatively low expression of ACE2 in the placenta. Existing studies investigating perinatal transmission and the impact of sexual intercourse have either involved small sample sizes or lacked statistical significance. This review aims to explore the current state of knowledge regarding the potential mechanisms of COVID-19 vertical transmission, identifying areas where further research is needed to fill the gaps in our understanding.

Neonatal outcomes of maternal prenatal coronavirus infection

The coronavirus disease 2019 (COVID-19) pandemic has led to significant changes in life and healthcare all over the world. Pregnant women and their newborns require extra attention due to the increased risk of adverse outcomes. Adverse pregnancy outcomes include intensive care unit (ICU) admission, pulmonary, cardiac, and renal impairment leading to mortality. Immaturity and variations of the neonatal immune system may be advantageous in responding to the virus. Neonates are at risk of vertical transmission and in-utero infection. Impaired intrauterine growth, prematurity, vertical transmission, and neonatal ICU admission are the most concerning issues. Data on maternal and neonatal outcomes should be interpreted cautiously due to study designs, patient characteristics, clinical variables, the effects of variants, and vaccination beyond the pandemic. Cesarean section, immediate separation of mother-infant dyads, isolation of neonates, and avoidance of breast milk were performed to reduce transmission risk at the beginning of the pandemic in the era of insufficient knowledge. Vertical transmission was found to be low with favorable short-term outcomes. Serious fetal and neonatal outcomes are not expected, according to growing evidence. Long-term effects may be associated with fetal programming. Knowledge and lessons from COVID-19 will be helpful for the next pandemic if it occurs. IMPACT: Prenatal infection with SARS-CoV-2 is associated with adverse maternal and neonatal outcomes. Our review includes the effects of COVID-19 on the fetus and neonates, transmission routes, placental effects, fetal and neonatal outcomes, and long-term effects on neonates. There is a growing body of data and evidence about the COVID-19 pandemic. Knowledge and lessons from the pandemic will be helpful for the next pandemic if it happens.

Trends in Mortality and Morbidities for Infants Born 24 to 28 Weeks in the US: 1997-2021

BACKGROUND

Mortality and morbidity for very preterm infants in the United States decreased for years. The current study describes recent changes to assess whether the pace of improvement has changed.

METHODS

Vermont Oxford Network members contributed data on infants born at 24 to 28 weeks' gestation from 1997 to 2021. We modeled mortality, late-onset sepsis, necrotizing enterocolitis, chronic lung disease, severe intraventricular hemorrhage, severe retinopathy of prematurity, and death or morbidity by year of birth using segmented relative risk regression, reporting risk-adjusted annual percentage changes with 95% confidence intervals overall and by gestational age week.

RESULTS

Analyses of data for 447 396 infants at 888 hospitals identified 3 time point segments for mortality, late onset sepsis, chronic lung disease, severe intraventricular hemorrhage, severe retinopathy of prematurity, and death or morbidity, and 4 for necrotizing enterocolitis. Mortality decreased from 2005 to 2021, but more slowly since 2012. Late-onset sepsis decreased from 1997 to 2021, but more slowly since 2012. Severe retinopathy of prematurity decreased from 2002 to 2021, but more slowly since 2011. Necrotizing enterocolitis, severe intraventricular hemorrhage, and death or morbidity were stable since 2015. Chronic lung disease has increased since 2012. Trends by gestational age generally mirror those for the overall cohort.

CONCLUSIONS

Improvements in mortality and morbidity have slowed, stalled, or reversed in recent years. We propose a 3-part strategy to regain the pace of improvement: research; quality improvement; and follow through, practicing social as well as technical medicine to improve the health and well-being of infants and families.

Sustained and Boosted Antibody Responses in Breast Milk After Maternal SARS-CoV-2 Vaccination

Background: Pregnant and lactating women were not included in the initial large vaccine clinical trials for SARS-CoV-2 (COVID) infection. Delineating the antibody titers in serum and breast milk of lactating women is important to determine the safety and benefits of vaccination in this special population. Objective: To investigate COVID vaccinations in breastfeeding dyads and effects on lactation, the Antibody Detection of Vaccine-Induced Secretory Effects trial (ADVISE) prospectively evaluated anti-COVID antibodies in serum and breast milk after initial paired and booster vaccines. Methods: This is a prospective longitudinal surveillance cohort study of lactating women. Eligibility criteria included ≥18 years of age, currently lactating, and at enrollment either received COVID vaccination within the past 60 days or planning vaccination within 60 days. Results: Among 63 lactating mothers, COVID vaccination led to breast milk secretory IgA (sIgA) and IgG antibodies with consistent viral neutralizing activity. Milk sIgA titers increased further after second vaccination and were prolonged after a third booster dose, including women with extended breastfeeding beyond 12 months. Milk IgG antibody titers were higher and more sustained than sIgA. Antibody titers were not associated with individual dyad characteristics or vaccine manufacturer. Vaccine-induced antibodies from milk were not detected in infant circulation. Conclusions and Relevance: Maternal COVID vaccination during lactation is well tolerated and generates sustained and boosted antibody responses in breast milk. COVID-specific sIgA and IgG antibodies with neutralizing activity are found in breast milk, including boosted mothers who continue breastfeeding beyond 12 months. These data support universal COVID vaccinations for all lactating mothers, including booster immunizations during extended breastfeeding (NCT04895475).

Breastfeeding provides a protective hug and the benefits have outweighed the risks during the COVID-19 pandemic

Mothers have been very hesitant about breastfeeding when they have COVID-19 infection or vaccinations. Maternal milk protects neonates through its high biological value, immune factors and anti-infectious molecules and this review shows that the virus that causes COVID-19 is not transmitted through breast milk. COVID-19 vaccines induce anti-spike antibodies with neutralising capacity, and phagocytosis, and no vaccine particles or messenger ribonucleic acid have been detected in breast milk. Most drugs used for maternal COVID-19 infections are safe for breastfed infants. CONCLUSION: The clear benefits of breastfeeding by far outweigh the very low risk of infant infections from COVID-19.

COVID-19 Disease in Under-5 Children: Current Status and Strategies for Prevention including Vaccination

Since the coronavirus disease (COVID-19) pandemic hit the globe in early 2020, we have steadily gained insight into its pathogenesis; thereby improving surveillance and preventive measures. In contrast to other respiratory viruses, neonates and young children infected with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) have a milder clinical presentation, with only a small proportion needing hospitalization and intensive care support. With the emergence of novel variants and improved testing services, there has been a higher incidence of COVID-19 disease reported among children and neonates. Despite this, the proportion of young children with severe disease has not increased. Key mechanisms that protect young children from severe COVID-19 disease include the placental barrier, differential expression of angiotensin-converting enzyme 2 (ACE-2) receptors, immature immune response, and passive transfer of antibodies via placenta and human milk. Implementing mass vaccination programs has been a major milestone in reducing the global disease burden. However, considering the lower risk of severe COVID-19 illness in young children and the limited evidence about long-term vaccine safety, the risk-benefit balance in children under five years of age is more complex. In this review, we do not support or undermine vaccination of young children but outline current evidence and guidelines, and highlight controversies, knowledge gaps, and ethical issues related to COVID-19 vaccination in young children. Regulatory bodies should consider the individual and community benefits of vaccinating younger children in their local epidemiological setting while planning regional immunization policies.