A vaccine for a baby who is too young to have one

Infants aged <6 months are not eligible for COVID-19 vaccination. They are
also, since the winter of 2022, hospitalised at **higher rates than any age
group except adults aged ≥65 years.**

The only route to protecting them is through their mother before they are born.

What the study found

The Overcoming COVID-19 Network ran a case-control study across **26
hospitals** during 9 March 2022 – 31 May 2023, through Omicron BA.1 to
XBB.1.16. Cases were infants under six months hospitalised with acute COVID-19
as the primary reason for admission; controls were infants hospitalised with a
similar illness who tested negative.

The protection is strongest when the baby is youngest — which is when they
are most at risk, and furthest from being able to be vaccinated themselves.

The number underneath the percentage

**Among 377 infants hospitalised with laboratory-confirmed COVID-19, 295
(78%) were born to women who had never received a COVID-19 vaccine dose.**

Among the case-patients 22% had a mother vaccinated during pregnancy,
against 28% of controls.

These were not fragile babies

Previously healthy infants accounted for 77% of the cases, and **critical
illness occurred in 13%** of them — life support, or death. Of the 716
hospitalised infants in the analysis, median age 2.3 months, only 21%
had any underlying health condition and 23% were born preterm.

This is not a disease that found the vulnerable children. It found the ones
who were too young for anything else.

Why the interval matters

**The median interval between the mother's most recent dose and the infant's
hospitalisation was 236 days** — most of a pregnancy plus the baby's first
months. For the infants under three months, where effectiveness was 54%, that
interval was shorter.

The report's own next question follows from it: **additional evaluations should
examine the effectiveness of updated vaccines and the impact of potential
waning immunity in infants aged ≥3 months.**

Who was left out, and why

360 of 1,076 eligible infants (33%) were excluded — and **288 of those
(80%) because their mother's most recent dose came before the pregnancy.** The
study is measuring a dose given during pregnancy, when antibodies cross the
placenta to the baby; a dose given earlier is a different exposure.

Also excluded: a single mRNA dose during pregnancy with nothing before it, a
dose within 14 days of delivery, a single viral-vector dose alone, and unknown
or unverifiable vaccination timing.

The finding, plainly

**Transplacental transfer of vaccine-induced antibodies has been
demonstrated**, and **maternal vaccination during pregnancy has not been
associated with increased risk of adverse pregnancy or infant outcomes.**

Expectant mothers should stay current with COVID-19 vaccination, which
protects them and, for the months when nothing else can, their infants.

Source: Centers for Disease Control and Prevention, MMWR.