We don’t know if this is due to Vaccines or post Covid:
https://www.brookings.edu/blog/up-front/2021/05/05/the-coming-covid-19-baby-bust-is-here/
It looks as if this data is from late 2020, so that is prior to the vaccine.
Of course, with a high percentage of the population both vaxxed and having been infected, any adverse effects are likely to be blamed by pro-vaxxers on the disease rather than the vaccine.