No association between COVID-vaccine and decrease in childbirth

Linköping University

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Toomas Timpka, professor of social medicine at Linköping University.

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Credit: Charlotte Perhammar/Linköping University

COVID-19 vaccination is not the cause behind a decrease in childbirth, according to a study from Linköping University, Sweden. The results speak against rumours about vaccination and reduced fertility. The findings have been published in the journal Communications Medicine.

“Our conclusion is that it’s highly unlikely that the mRNA vaccine against COVID-19 was behind the decrease in childbirth during the pandemic,” says Toomas Timpka, professor of social medicine at Linköping University.

The researchers investigated the issue because, since the beginning of the COVID-19 pandemic, unfounded rumours have circulated, especially on social media, alleging that vaccination impairs chances of becoming pregnant. In the later stages of the pandemic, there was a decrease in the number of children born in some countries, including Sweden. This raised the question whether this could be due to the new vaccines.

In the study, the researchers analysed all women aged 18 to 45 years in Region Jönköping County, a total of almost 60,000 women (of the region's total population of 369,000 people). Of these women, 75 per cent were vaccinated once or more against COVID-19 from 2021 to 2024. The researchers used data on childbirths, vaccination, miscarriages and deaths from healthcare records.

When the researchers compared childbirths and miscarriages between vaccinated and unvaccinated women, they found no statistically significant difference between the groups. This is in line with several previous studies that have not found any association between COVID vaccine and fertility.

“We see no difference in childbirth rates between those who have taken the vaccine and those who haven’t. We’ve also looked at all registered miscarriages among those who became pregnant, and we see no difference between the groups there either,” says Toomas Timpka.

The researchers believe that the decrease in childbirth has other, more likely explanations. Those who are now in their 30s, an age when it is most common to have children, were born in the second half of the 1990s. This was a time of financial difficulties and declining childbirth rates in Sweden. In other words, the group of current potential parents has become smaller due to declining birthrates 30 years earlier. Also, factors linked to the pandemic may have reduced childbirth, such as health and economic concerns and changed behaviour during lockdown.

One of the strengths of the study is that it examines pregnancy outcomes in a large group that is representative of the country’s population. The researchers have taken into account that the woman’s age is a possible factor that could hide a possible effect of vaccines on childbirth, and they have therefore compensated for age in their analysis.

The study received financial support from, among others, the Swedish Research Council.

Article: COVID-19 vaccination carries no association with childbirth rates in Sweden, Dennis Nordvall, Thomas Schön, Jorma Hinkula, Olle Eriksson, Armin Spreco, Örjan Dahlström, Johan Lyth, Daniel Axelsson, Elin Gursky, Marie Blomberg and Toomas Timpka, (2026), Communications Medicine, published online 21 January 2026, doi: https://www.nature.com/articles/s43856-026-01396-x

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Journal

Communications Medicine

DOI

10.1038/s43856-026-01396-x 

Article Title

COVID-19 vaccination carries no association with childbirth rates in Sweden

 

Model connects animal movement and population dynamics

Brazilian-German collaboration closes gap in theoretical ecology

Helmholtz-Zentrum Dresden-Rossendorf

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For planning animal conservation measures, it is vital to know where endangered species live and how they interact. Ecologists are successfully using tracking technology to learn about the movements of individual animals. Yet, leveraging this knowledge to understand how entire populations change in space and time, including long-term persistence and survival chances in a given area, remains a long-standing open question in ecology. A major step toward answering this question was now achieved through a collaboration between researchers from São Paulo State University (UNESP, Brazil) and the Center for Advanced Systems Understanding (CASUS) at Helmholtz-Zentrum Dresden-Rossendorf (HZDR): The scientists introduced a new theoretical framework that shows how individual animal movements and their home ranges shape population dynamics across space and time (Ecology Letters, DOI: 10.1111/ele.70269).

Despite decades of independent progress in population ecology and movement ecology, researchers have lacked a theoretical bridge between these two disciplines. “Ecologists have been trying to establish this link since the 1950s, when they started to characterize animal movement patterns,” says Dr. Ricardo Martinez-Garcia, head of the CASUS Young Investigator Group “Dynamics of Complex Living Systems” and senior author of the study. Classic population dynamics models, going back to Pierre François Verhulst’s work in 1838, describe how populations grow until they reach the limits imposed by available resources, such as food and space, but overlook the importance of animal movement in determining these saturation patterns. “In many cases, observed population sizes could not be explained with existing theoretical frameworks. We were confident that incorporating the movement behavior of individual animals we observe in tracking data could solve these discrepancies,” adds Martinez-Garcia.

Ecologists have long known that animals use their habitats non-uniformly and spend most of their lives within home ranges that are substantially smaller than the population range. In recent years, technological and methodological advances have provided unprecedented insight into how organisms move, including a more precise quantification of their home ranges. Central to this progress are statistical methods developed with key contributions from Prof. Justin M. Calabrese, co-author of the study and head of the Earth System Science department at CASUS. “A major innovation of our theory is that it allows the prediction of population dynamics to be based on the same animal movement model that is widely used to estimate home ranges from tracking data. This means that, under the hood, home-range estimation and population modeling can now be powered by the same engine, which gives our theory a stronger connection to data and leads to better-informed, real-world conservation recommendations,” says Calabrese.

Model incorporates interactions between more than two animals

A 2020 study led by Martinez-Garcia already linked individuals’ exact use of their home ranges, their so-called range-residency, to the frequency of interactions between two animals. It showed that encounter rates can deviate strongly from those predicted by classical models that oversimplify movement. The next logical step was moving from pairs to a larger number of animals. In this way, the theoretical framework would be able to account for demographic processes driven by cooperation, competition, reproduction and other animal interactions. But this change of scale in the study represented a significant challenge: “When we have an entire population of animals, each one will have its own movement behavior and the number of possible interactions becomes enormous very quickly,” says Rafael Menezes, a postdoctoral researcher at UNESP and former PhD student at Martinez-Garcia’s group.

The extended framework, named range-resident logistic model, manages this complexity elegantly by introducing a so-called crowding index that summarizes all relevant information about how movement shapes animal interactions. Menezes continues: “This coefficient, which can be readily calculated from animal tracking data, gives an indication of how animals in a population interact: are they avoiding each other, are they trying to spend more time close to each other, or are they somewhat indifferent?”

The direct comparison of the new and old models clearly indicates, as foreseen, a highly relevant impact of the movement data: Depending on the selected parameter conditions, population size predicted by the range-resident logistic model is sometimes twice, sometimes half the size of that predicted by the classical Verhulst equation. “A difference that can make a difference,” comments Martinez-Garcia. According to him, the new model is important when practical conservation questions are investigated, such as the impact of human infrastructure on the fate of wildlife populations. “One particular case we are currently working on is the question of what happens to a population when a new highway cuts through the animal’s habitat. Specifically, we are talking about Brazilian tapirs here. Only thanks to an accurate description of animal movements, we can quantify wildlife vehicle collisions and estimate viability of the tapir population.”

Brazilian scientist joins CASUS

Brazilian native Rafael Menezes is a postdoctoral researcher at the International Center for Theoretical Physics-South American Institute for Fundamental Research (ICTP-SAIFR), an international research center based at the Institute of Theoretical Physics of UNESP and supported by the São Paulo Research Foundation, FAPESP. Still a PhD student two years ago, Menezes was awarded competitive funding from the Brazilian federal agency CAPES to continue his doctoral research, supervised by Martinez-Garcia, in Görlitz. Menezes successfully defended his doctoral thesis at University of São Paulo’s Institute of Biosciences in early 2025.

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Journal

Ecology Letters

DOI

10.1111/ele.70269 

Method of Research

Computational simulation/modeling

Subject of Research

Animals

Article Title

The Range-Resident Logistic Model: A New Framework to Formalise the Population-Dynamics Consequences of Range Residency

 

Large study shows scaling start-ups risk increasing gender gaps

Stockholm School of Economics

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Mohamed Genedy, Postdoctoral Fellow, Stockholm School of Economics 

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When startups scale quickly, founders often make hurried hiring decisions that unintentionally disadvantage women, according to new study from the Stockholm School of Economics in Sweden. The study shows how the pressures of rapid growth increase the likelihood that founders rely on mental shortcuts and make biased decisions. 

Drawing on large‑scale Swedish data, the study shows that scaling—when companies hire far more people than their usual growth trend would predict—puts pressure on founders to decide swiftly, which increases the use of mental shortcuts. These shortcuts can activate gender stereotypes, shaping who gets hired and who moves into managerial roles.  

“During those moments of rapid growth, even well‑intentioned leaders can fall back on familiar stereotypes when assessing who they believe is best suited for the role,” says Mohamed Genedy, co-author and Postdoctoral Fellow at the House of Innovation, Stockholm School of Economics. 

Reduced odds of hiring female managers 

His research analyzes more than 31,000 new ventures founded in Sweden between 2004 and 2018. It finds that in male‑led startups, scaling reduces the odds of hiring a woman by about 18 percent, and the odds of appointing a woman to a managerial position by 22 percent.  

These patterns emerge even in a highly gender‑equal national context, making the findings especially noteworthy.  

Crucially, the study reveals that founders with HR‑related education counteract these challenges. In ventures led by founders with HR training, the odds of hiring a woman increase by more than 30 percent, and the odds of appointing a woman to a managerial role increase by 14 percent for the same level of scaling.  

“When founders have experience with structured hiring practices, the gender gaps shrink, and in some cases even reverse,” Genedy says.  

“This shows that getting the basics of HR right early on really pays off. When things start moving fast, founders with HR knowledge are less likely to rely on biased instincts and more likely to hire from a broader talent pool.”  

Prior experience in companies with established HR practices also helps, though less so. It raises the likelihood of hiring women as the new ventures scale, but does not significantly affect managerial appointments. 

Differences persist in female-led ventures 

The study additionally shows that these patterns are not driven by founder gender alone. Even solo female‑led ventures display similar tendencies when scaling, though to a somewhat lesser degree.  

And in female‑dominated industries, scaling increases the hiring of women for regular roles but still reduces the likelihood that women are appointed into managerial positions.  

“When scaling accelerates, cognitive bias kicks in for everyone,” says Mohamed Genedy. “Female founders are not immune to these patterns.”  

Together, these results point to underlying cognitive mechanisms that shape decisions under time pressure. 

The study was funded with support from Jan Wallanders and Tom Hedelius Stiftelse, Tore Browaldhs Stiftelse and the Kamprad Family Foundation for Entrepreneurship, Research and Charity. 

Publication  
Genedy, M. (2026). Scaling with Bias? The role of founders’ HR knowledge and experience in hiring and managerial appointments.  Human Resource Management 
 
About the Stockholm School of Economics  
The Stockholm School of Economics is rated as a top business school in the Nordic and Baltic countries and enjoys a strong international reputation. World-class research forms the foundation of our educational offering, which includes bachelor, master, PhD, MBA, and Executive Education programs. Our programs are developed in close cooperation with the business and research communities, providing graduates substantial potential to attain leading positions in companies and other organizations. 

The School is accredited by EQUIS, certifying that all of its principal activities – teaching as well as research – maintain the highest international standards. The Stockholm School of Economics is also the only Swedish member institution of CEMS and PIM, which are collaborations between top business schools worldwide, contributing to the level of quality for which our school is known. 

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Journal

Human Resource Management

DOI

10.1002/hrm.70056 

Method of Research

Observational study

Subject of Research

People

Article Title

Scaling with Bias? The role of founders’ HR knowledge and experience in hiring and managerial appointments

Article Publication Date

1-Feb-2026

Navigating academic integrity in biomedical research: The impact of large language models on current practices and future directions

FAR Publishing Limited

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Large language models are predominantly applied in four major academic domains: (1) Research Paper Writing Assistance: LLMs facilitate manuscript preparation through translation services, comprehensive proofreading, and multiple perspective analysis, while simultaneously managing auxiliary tasks such as data organization, thereby substantially enhancing research productivity. (2) Research Data Analysis Support: LLMs exhibit emerging capabilities in dataset compilation, analytical processing, and automated code generation, leading to significant improvements in research efficiency. (3) Academic Visualization Generation: LLMs enhance the traditional visualization process through automated generation of scientific illustrations and data representations, facilitating more effective communication of research findings. (4) Academic Peer Review Support: LLMs contribute to both manuscript self-assessment and formal review processes by providing systematic content evaluation and generating structured review feedback.This figure was created based on the tools provided by Biorender.com (accessed on 20/08/2025)

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Credit: Anqi Lin, Zuwei Chen, Aimin Jiang, Bufu Tang, Chang Qi, Lingxuan Zhu, Weiming Mou, Wenyi Gan, Dongqiang Zeng, Mingjia Xiao, Guangdi Chu, Shengkun Peng, Hank Z.H. Wong, Lin Zhang, Hengguo Zhang, Xinpei Deng, Quan Cheng, Jian Zhang, Peng Luo

As Large Language Models (LLMs) continue to advance, they have garnered widespread public attention and extensive application across numerous industries and academic disciplines. The proliferation of LLMs has sparked considerable research interest, with studies primarily focusing on their technical characteristics and specific application scenarios. However, systematic research examining the impact of LLMs on academic integrity remains relatively scarce. Academic integrity is of paramount importance in the biomedical field. Therefore, this paper aims to examine both the opportunities and challenges that LLMs present to academic integrity in the biomedical field, and proposes solutions for optimizing the beneficial applications of LLMs. From a positive perspective, LLMs offer substantial benefits to researchers by enhancing research efficiency, improving research quality, and facilitating the generation and dissemination of academic insights. However, they also present numerous challenges, including the potential for promoting academic misconduct, generating content inaccuracies or ambiguous expressions, introducing bias and fairness concerns, compromising peer review mechanisms, facilitating the dissemination of misinformation, and undermining higher education—all of which demand careful attention. To address these issues, we propose solutions and feasible strategies centered on ten core dimensions: establishing policies and regulatory guidelines, enhancing AI literacy and application capabilities, developing and improving relevant technical tools, establishing human-AI collaboration models, reforming peer review procedures and academic evaluation systems, promoting international cooperation and standardization, increasing transparency and strengthening disclosure, reinforcing professional ethics education, and advancing artificial intelligence detection technologies. Overall, while LLMs undoubtedly pose challenges for maintaining academic integrity, their potential for positive impact remains promising. It is anticipated that with technological advancement and improved ethical standards, LLMs will ultimately preserve and strengthen academic integrity.

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Journal

International Journal of Surgery

DOI

10.1097/JS9.0000000000003839 

Method of Research

Literature review

Article Title

Navigating Academic Integrity in Biomedical Research: The Impact of Large Language Models on Current Practices and Future Directions

FREYA'S DAY SCIENCE DUMP

THE CREATOR, IF HE EXISTS, IS INORDINATELY FOND OF BEETLES
AND STARS

J.B.S HALDANE