DP and I both had booster shots done when DS was about 3 weeks old. I am fully breastfeeding him.

My mum and my MIL also got booster shots after he was born and both had contact with him when he was about 6 weeks old.

Nil negative effects or side effects here. My town has a massive outbreak of WC atm so we all decided the risks of vacinating were outweighed by the risk of contracting it when he was so young.