A November 5 study of about 11 million infants found that recorded vitamin K use fell from 97.7% in 2017 to 95.0% in 2025.
Daylight Post found that the two papers measure different outcomes in overlapping records. Their case totals cannot be added together.
Why a newborn needs the shot
Vitamin K helps blood form clots, which stop bleeding. Deficiency means not having enough of the vitamin. Babies are born with very little stored in their bodies. Without enough, they can bleed inside the gut or brain, where a parent may not see the problem.
The Centers for Disease Control and Prevention (CDC), the US public-health agency, says bleeding caused by vitamin K deficiency can occur in otherwise healthy babies up to six months old. Part of the birth dose acts immediately; the rest is released slowly over the next two to three months.
The shot supplies a vitamin, not a vaccine. The CDC says staff should discuss the dose with expectant parents before they reach the delivery room, giving families time to understand its purpose.
What happened after babies went home
JAMA, a medical journal, studied 5.2 million babies, comparing bleeding after discharge through six months with and without a recorded shot.
| Birth injection recorded | Babies with bleeding per 10,000 |
|---|---|
| No | 10.3 |
| Yes | 4.8 |
After accounting for measured differences, researchers found roughly twice the risk in the group without a recorded shot. This covers several bleeding diagnoses, not all confirmed as caused by vitamin K deficiency.
The two studies do not count the same thing
The related medical journal JAMA Pediatrics tracked diagnoses specifically recorded as vitamin K-related bleeding. They rose from 24.0 to 107.4 per 100,000 infants between 2017 and 2025. Most were diagnosed in the first week of life.
Both use Epic Cosmos, a system pooling participating health services’ medical records. Different selection rules produced different groups. Their figures do not count every American baby.
Missing records do not prove refusal. Diagnoses may be miscoded. These records show an association, rather than proving what caused every bleed.
For parents, the timing matters: leaving hospital in good health does not end the risk. The CDC advises discussing vitamin K with the baby’s healthcare provider. Waiting for visible bleeding can mean waiting until a serious problem has already developed.