Association between the COVID-19 vaccination campaign and fertility trends: a population-level time series analysis for 22 countries.

Introduction: At the turn of 2021-2022, monthly birth rates declined in many higher-income countries. We explore how the rollout of COVID-19 vaccination was associated with this decline. Methods: Using an interrupted time series design, we evaluate the impact of the onset of the COVID-19 pandemic and the start of COVID-19 vaccination on seasonally adjusted monthly total fertility rates in 22 high-income countries. We study the associations between COVID-19 vaccination and fertility by additionally controlling for youth unemployment, stringency index and vaccination coverage. Fertility data come from the Short-Term Fertility Fluctuations data series under the Human Fertility Database. Indicators used as control variables originate from Eurostat and OECD databases, Oxford COVID-19 Government Response Tracker and Our World in Data. Results: The start of the pandemic had an immediate effect on fertility in most countries, although the size and direction of level changes considerably varied across them. The impact of COVID-19 vaccination was likewise extensive. While a relatively pronounced negative association between the COVID-19 vaccine rollout and fertility 9 months later was found only for 10 out of 22 countries, indications of a negative fertility response were detected in the vast majority of countries. For several countries, the decline was preceded by fertility increase that took place after the onset of the pandemic. Only 4 out of 22 countries had post-vaccination fertility declines that resulted in fertility being on lower level than what the pre-pandemic trend predicted. Additional control variables changed the associations only a little. Conclusions: The COVID-19 vaccination campaign contributed to the variation in short-term fertility trends. Several countries experienced declines following the campaign, which often returned fertility closer to the pre-pandemic trend. Fertility appears to have responded in short run to vaccination, but only in few cases such that the long-term trajectory is below the pre-pandemic trend.