Background: Vaccination against COVID-19 is an effective measure to mitigate the pandemic. Pregnant and breastfeeding women were not included in registration studies, so official recommendations to vaccinate this vulnerable group appeared belated. Therefore, our aims were to evaluate vaccination uptake, reasons for and against vaccination, and the changes in these depending on the official national recommendations in Germany. Methods: An anonymous online cross-sectional survey among pregnant and breastfeeding women was conducted prior to and after the publication of the official vaccination recommendation. Results: Data from the convenience sample of 5411 participants (42.9% pregnant; 57% breastfeeding) were analysed. The recommendation was known to 95% of the participants. The information was obtained mainly autonomously (61.6%) and through the media (56.9%). Vaccination uptake increased in pregnant (2.4% before vs. 58.7% after) and breastfeeding women (13.7% vs. 74.7%). As reasons to get vaccinated, pregnant women indicated more fear of the infection than of the side effects of vaccination (52.0% before vs. 66.2% after), intended protection of the baby and oneself (36.0% vs. 62.9%), and limited information about vaccination (53.5% vs. 24.4%). Conclusion: The official national recommendation is widely known and mostly obtained autonomously, thereby showing a high level of awareness and a rise in vaccination uptake. Nonetheless, targeted education campaigns focusing on scientific evidence should be maintained, whereas the engagement of health professionals should be enhanced.