Is this the case in the United States, where the CDC makes recommendations?
And if so, why not administer it only to those children of mothers who test positive?
We don't put everyone on a statin simply because most (i.e. more than half of) people will eventually develop heart disease. Instead, we test and administer statins to only those people who have heart disease risk factors.
We don't give everyone bariatric surgery or weight loss drugs simply because most Americans are overweight or obese. Instead, these remedies are administered only to those who are most likely to benefit.
No drug or vaccine is without side effects. It's clear that there's no such thing as informed consent in today's world. The patient cannot be informed because the side effects are hidden from him. And he definitely hasn't consented if coercion was involved in his decision to receive the treatment.