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Vaccination, immunity, and the changing impact of COVID-19 on infant health
Florencia Torche1, Jenna Nobles2
1Department of Sociology, Stanford University, Stanford, CA 94305.
Insights
Maternal COVID-19 infection significantly increased preterm birth risk early in the pandemic. This risk disappeared by 2022, particularly in highly vaccinated areas, suggesting vaccines prevented many infant health issues.
Area of Science:
- Epidemiology
- Maternal and Child Health
- Infectious Disease Dynamics
Background:
- In utero exposure to COVID-19 (coronavirus disease 2019) poses risks to infant health, with impacts evolving due to variants, immunity, and vaccination.
- The timing of infection during pregnancy is critical, alongside the presence of vaccination, influencing outcomes like preterm birth.
Purpose of the Study:
- To estimate the causal impact of maternal COVID-19 infection on preterm birth.
- To analyze how this impact changed from 2020 to 2023.
- To evaluate the protective effect of COVID-19 vaccination on infant health outcomes.
Main Methods:
- Utilized population-level data with universal maternal COVID-19 infection information and linked sibling data for a quasi-experimental design.
- Assessed changes in the association between prenatal COVID-19 infection and preterm birth from 2020 to 2023.
- Examined the moderating role of vaccination rates at the zip code level.
Main Results:
- Prenatal COVID-19 infection was substantially linked to an increased probability of preterm birth.
- The adverse effect of infection on preterm birth was significant in 2020-2021 but diminished by 2022.
- Harmful impacts resolved nearly a year sooner in areas with high vaccination rates, implying vaccine-prevented preterm births.
Conclusions:
- Maternal COVID-19 infection poses a significant, time-varying risk to infant health, specifically preterm birth.
- COVID-19 vaccination appears to mitigate the adverse effects of infection, potentially preventing thousands of preterm births.
- Ongoing monitoring of infectious disease impacts and proactive mitigation strategies are crucial for protecting vulnerable populations.
Abstract:
In utero exposure to COVID-19 infection may lead to large intergenerational health effects. The impact of infection exposure has likely evolved since the onset of the pandemic as new variants emerge, immunity from prior infection increases, vaccines become available, and vaccine hesitancy persists, such that when infection is experienced is as important as whether it is experienced. We examine the changing impact of COVID-19 infection on preterm birth and the moderating role of vaccination. We offer the first plausibly causal estimate of the impact of maternal COVID-19 infection by using population data with no selectivity, universal information on maternal COVID-19 infection, and linked sibling data. We then assess change in this impact from 2020 to 2023 and evaluate the protective role of COVID-19 vaccination on infant health. We find a substantial adverse effect of prenatal COVID-19 infection on the probability of preterm birth. The impact was large during the first 2 y of the pandemic but had fully disappeared by 2022. The harmful impact of COVID-19 infection disappeared almost a year earlier in zip codes with high vaccination rates, suggesting that vaccines might have prevented thousands of preterm births. The findings highlight the need to monitor the changing consequences of emerging infectious diseases over time and the importance of mitigation strategies to reduce the burden of infection on vulnerable populations.
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