The Psychological Effects of Maternal COVID-19 Vaccination on Babies: Impact on Psychological Interactions Between Mothers and Infants

Written by: Omar ElDimassi

Edited by: Ariel Yu, Akshay Pokala, Emily Wang 

Illustrated by: Caroline Shen

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Abstract

The COVID-19 pandemic led to widespread vaccination efforts, extending to pregnant individuals. However, some people worry that the vaccine could affect newborn babies. Many also have concerns  about its impact on babies' mental and social development, especially their postnatal bonding. Recent studies help explain how the vaccine works and what impacts it may have on infant development. Research indicates that maternal vaccination does not appear to negatively affect cognitive, motor, or sensory abilities of infants, nor does it pose significant health risks in the development of hearing or mental health.

Introduction

The COVID-19 mRNA vaccine was an important scientific achievement, helping people avoid serious illness from the virus. The vaccine uses mRNA to teach the body how to recognize and fight the virus. When the vaccine was first introduced, pregnant individuals were excluded from most studies, raising concerns about the vaccine’s effect on fetal development. However, concerns over maternal vaccination are not new. People have long worried about how medical treatments during pregnancy might affect babies before birth. For instance, concerns about medications like thalidomide (a drug that caused birth defects) — a widely used drug to treat nausea in pregnant women — and vaccines such as those for influenza have shaped the way people view maternal vaccination today, making some people more cautious about new vaccines during pregnancy. This caution comes from past experiences where medications like thalidomide caused serious birth defects and where some early vaccines raised concerns about potential risks to fetal health. During pregnancy, the mother's immune system can affect the baby's development. If the vaccine causes a strong immune response, it might impact fetal brain development known as maternal immune activation, this has been linked to developmental problems in other infections [1]. However, it's difficult to tell whether any changes in babies come from the vaccine or from the virus itself [2]. Research shows that when a pregnant person’s immune system is strongly activated, it can sometimes affect the baby’s development, leading to conditions like autism spectrum disorder (ASD) or other mental disorders like schizophrenia in extreme cases [1]. That said, not all instances of immune activation result in negative outcomes, and many pregnancies proceed without complications. Because of this, many people were initially hesitant about COVID-19 vaccines during pregnancy, fearing unknown long-term effects on the baby’s brain and behavior.

Maternal Vaccination and Infant Neurodevelopment

A study by Dr. Jaswa at JAMA Pediatrics in 2024 looked at how babies whose mothers were vaccinated during pregnancy developed over time. The researchers used a survey called the Ages and Stages Questionnaire (ASQ-3) to measure over 2,000 babies' skills at 12 and 18 months. At 12 months, the data showed no significant difference in development between the two groups;at 18 months, the results remained consistent, further confirming that vaccination did not increase the risk of developmental delays [3]. While these findings are reassuring, Dr. Jaswa notes that follow-ups are needed to fully understand the effects in the long term.

A similar recent study conducted in Scotland in 2025, which assessed nearly 25,000 infants, also found no developmental delays linked to maternal COVID-19 vaccination [4]. The study examined cognitive, motor, and social skills at 13 to 15 months and concluded that vaccinated mothers did not pass any negative effects onto their babies. However, researchers are still studying whether immune responses during pregnancy affect children’s brain development over time [1].

Maternal Vaccination and Sensory Outcomes

Some viruses can cause hearing problems in babies, such as cytomegalovirus (CMV), a herpes virus that can be transmitted to the fetus during pregnancy. They can infect the developing fetal cells and interfere with normal development, which led scientists to question whether the COVID-19 vaccine might have a similar effect [2]. The COVID-19 Mother Baby Outcomes Study (COMBO) from Columbia University tested whether babies exposed to COVID-19 during pregnancy were at a higher risk of hearing loss. The researchers compared babies whose mothers had COVID-19 during pregnancy to those whose mothers did not. They used newborn hearing tests done in hospitals and surveys filled out by mothers when their children were 2 to 3 years old. The study found that both groups of babies had similar hearing results, showing no difference between those exposed to COVID-19 and those who were not [2].

While these results are reassuring, hearing loss is only one aspect of sensory development. Some researchers are now investigating whether maternal vaccination affects vision, touch sensitivity, or even babies' responses to social stimuli. Preliminary findings suggest no major differences, but further research is needed to confirm whether other early sensory behaviors are influenced by maternal immune activation.

Psychological Interactions between Mothers and Infants 

Additionally, how mothers and babies interact is an important part of early development. Some studies show that inflammation during pregnancy can affect how babies interact with others, such as being less responsive to social cues or having difficulty forming attachments later in life. However, there is no clear research yet showing that the COVID-19 vaccine changes how mothers and babies bond. The same initiative, COMBO, is focusing on computational biology and understanding code links with babies' and mothers' behaviors. Researchers code certain interactions with mothers and babies and, through molecular testing, work towards answering the question of whether there is a difference between babies whose mothers were vaccinated and those whose mothers were not. These 'code links' refer to a system where researchers assign specific letters to moments in video recordings to track particular behaviors or traits. For example, when studying a baby's smile, researchers may mark certain moments with a code to indicate whether the baby is smiling, not smiling, and so on. These codes help researchers track and measure behaviors, making it easier to spot patterns and changes over time.

Beyond biological concerns, researchers are also studying the psychological effects of maternal vaccination on babies. Many parents reported heightened stress and anxiety during the pandemic, which could indirectly affect their interactions with their babies. Studies have shown that maternal stress during pregnancy can influence babies' temperament, making them more prone to fussiness or difficulties in emotional regulation [3]. However, it remains unclear whether this stress stems from the vaccine itself or the overall uncertainty and isolation of the pandemic [4]. A 2024 study from Developmental Psychology suggested that pandemic-born infants may exhibit different social behaviors compared to pre-pandemic cohorts, but these effects were more strongly linked to environmental stressors rather than vaccination.

It's important to remember that the pandemic itself caused a lot of stress for parents, and such periods affected the mental health of many individuals. Isolation, anxiety, and changes in daily routines are all factors that could’ve  affected babies' mental health. This makes it difficult to determine if the changes are from the vaccine or from the other factors present  during pandemic.

Conclusion

Based on current evidence, the COVID-19 vaccine does not seem to harm babies' brain development or sensory motor. The studies from JAMA Pediatrics and the COMBO Initiative provide reassurance; however, scientists still need to study the long-term effects of the vaccine on babies' mental health and social interactions. Understanding how maternal health, immune responses, and environmental factors interact will help doctors provide better advice to pregnant individuals in the future.

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References

[1] Hardie I;Marryat L;Murray A;King J;Okelo K;Boardman JP;Lombardo MV;Stock SJ;Wood R;Auyeung B; “Early Childhood Developmental Concerns Following SARS-COV-2 Infection and Covid-19 Vaccination during Pregnancy: A Scottish Population-Level Retrospective Cohort Study.” The Lancet. Child & Adolescent Health, U.S. National Library of Medicine, 9 Mar. 2025, pubmed.ncbi.nlm.nih.gov/39978991/#:~:text=Interpretation%3A%20SARS%2DCoV%2D2,of%20early%20childhood%20developmental%20concerns. 

[2] Ahmed, I., Yu, M., Chaves, V., Xu, R., Lavallée, A., Warmingham, J.M., Firestein, M., Kyle, M.H., Fisher, K., Merriman, E.T., Rodriguez, C., Mace, W., Fernandez, C., Dumitriu, D. and Lalwani, A.K. (2025), Risk of Hearing Loss in Neonates and Toddlers within Utero Exposure to SARS-CoV-2. The Laryngoscope, 135: 385-392. https://doi.org/10.1002/lary.31739

[3] Jaswa EG, Cedars MI, Lindquist KJ, et al. In Utero Exposure to Maternal COVID-19 Vaccination and Offspring Neurodevelopment at 12 and 18 Months. JAMA Pediatr. 2024;178(3):258–265. doi:10.1001/jamapediatrics.2023.5743

[4] “Covid and Vaccines Not Linked to Early Child Development Issues.” The University of Edinburgh, 19 Feb. 2025, www.ed.ac.uk/news/covid-and-vaccines-not-linked-to-early-child-development-issues#:~:text=A%20study%20of%20almost%2025%2C000,contracting%20the%20virus%20during%20pregnancy.